Tower Defense has managed enough games to become a genre. In a TD game, the objective is simple: keep the enemies, typically called "creeps", from managing to fully traverse the path by placing guards, usually towers (hence the name), to take them out. The penalty for an enemy getting through varies between games and enemy types, but you certainly don't want too many enemies to get through or it's game over.
Kingdom Rush seems to be another standard TD game that tries to rely on medieval weaponry to appeal to the audience, but it makes use of one thing, among the basics, to set itself apart from other TD games: the Barracks mechanic. This is a useful trait for various reasons that will be pointed out throughout this exploration. In order to do the game's design justice, we have to start by taking a good look at each level.
Level 1: Southport
In order to get the player into the game, the developers start off with something easy. They take the time to make sure you learn how to play. The enemies in Southport are pitifully easy to deal with, as most setups can defeat them without issue. Rest assured that things will get harder.
One mechanic to talk about is early calling. You can click on the enemy icon for the next wave whenever you like before it's inbound to let it in early. The benefit of doing so is free Gold equal to the number of seconds left before the wave would have come in naturally, and added recharge to spells (see below, again equal to the number of seconds left. You will have more enemies to deal with if you haven't already routed the current wave, of course, but if you win through this adversity, you get better reward for the risk you take.
Another mechanic to note in Kingdom Rush is the Strategic Points. Most TD games are more freeform about where you can place towers, but KR restricts you to certain locations near the road in where you can place them. This is probably because of programming limitations involving the Barracks mechanic, but nevertheless, if you spam cheap buildings, you will run out of locations to place more of them.
The 4 basic tower types are as follows: Archer Towers are inexpensive and have a good rate of fire, Mage Guilds deal high damage that pierces armor, Artillery Towers (which will be called cannons) deal area damage, and Barracks sends out 3 soldiers who block enemies.
The first 3 are standard fare for TD games, but Barracks are, as mentioned, what makes Kingdom Rush unique. What the soldiers that come out of them do is engage enemies in melee combat, which forces them to stop. It is no coincidence that the first wave sends out 3 Goblins, who will be stopped completely by the 3 soldiers; Ironhide Studios wants you to see the appeal of the Barracks mechanic. Goblins are ideal because they have still better than par mobility to prevent cost-effective victory with anything else, but lack the power to deal with even the most basic of soldiers.
Each soldier stops only one enemy tops, but if your own soldiers outnumber the enemies, multiple soldiers will attack the same enemy with only one of them getting hurt. The melee lock can be broken only by one of 3 methods:
*Your soldiers are defeated by their HP being reduced to 0. Note that as soon as the enemies outnumber your soldiers, any who were previously melee locked by now removed soldiers will start continuing along the path.
*The enemies are defeated by their HP being reduced to 0. A soldier who was meleeing a now slain enemy will search for any new targets to engage.
*The Barracks for your soldiers has its Rally point reset to a different location.
This brings up the Rally command. A given Barracks building places its 3 soldiers around a location along the path, and the soldiers wait for enemies to draw near enough the location before charging into battle. This location can be changed by the Rally command. The location can only be set within the Rally Range of a Barracks, which is more or less Averege-level attack range for other towers. For a certain value of Average, but that's getting into considerable details, certainly earlier than I should.
Additionally, the player gets 2 spells, each with a numbered hotkey. First up is Rain of Fire (hotkey 1). It drops 3 meteors onto a designated spot, each meteor dealing about 45 damage regardless of defenses to each and every enemy in that location. This can be used to clear up a thick group of enemies in a pinch. However, it takes 80 seconds to recharge, which is a good deal of time. Reinforcements (hotkey 2) is much faster, taking only 10 seconds to recharge. It drops 2 farmers wherever you like along the path. It can be used to place road guys wherever you desperately need them, but keep in mind that the farmers each have only 30 HP, 1-2 ATK, and no armor.
You can see a sharp contrast to Bloons Tower Defense 5, which itself compared to other TD games even has micromanagement, but it's much less intensive about it than Kingdom Rush is in favor of more macromanagement. The most obvious comparison is BTD5's Road Spikes VS KR's Reinforcements: BTD5's Road Spikes $30 a pile to pop upwards of 10 RBE worth, not exactly cost effective, though you can spam them if you're desperate, which ends up justifying the Spike Factory's above average cost as a way to prevent players from just avoiding this. KR's Reinforcements is more along the lines of a player's individual move, as it doesn't cost any money but instead can't be spammed because of the cooldown. Additionally, the closest BTD5 has to the Barracks buildings is the Ice Tower, but that can actually backfire in more ways than the Barracks in KR can do so, can't be controlled directly, and has issues with catching things like Pinks. That last one is going to be relevant soon enough. BTD5 does have a micromanagement tower, however: the Dartling Gun, which can be used to hit whatever you like wherever you like in general. Even then, the Dartling Gun is expensive, in addition to requiring an upgrade to fix accuracy issues, though let's be fair: the Dartling DOES have stellar potential.
With the BTD5 comparisons out of the way, we can now talk about Southport's level general level design. To make sure things aren't too terribly hard, most of the enemies are Goblins, which if you couldn't tell are the game's variant of the Goombas you know and love from the Mario games. What makes them able to cause problems is that they have decent mobility and additionally can come in large groups. To make sure that things stay interesting, the game has to throw more threatening enemies. Not surprisingly, the second enemy type, the Orc, is able to take punishment. In addition to considerably higher HP, they're also equipped with armor, prodding the game to make sure you know that mages fire shots that ignore the armor, which actually happens by targeting the Magic DEF stat, which if you're familiar with general medieval style games shouldn't be too much of a shocker, since they do love them their magic.
Since only 2 enemy types have appeared, you can bet that enemy setups will be different between levels. Keep in mind that armor enemies appear in every level in the game, and even provide a theme to the general level design, but for us to truly understand what it is, we have to look at the levels closely.
Level 2: The Farmlands
A tip provided upon starting the level is that soldiers are to be supported by range fire to take advantage of the fact that the enemies are stopped, while simultaneously keeping their low attack power from being too much of a weakness. This tip is provided especially in light of one important factor: the micromanagement expectation that Kingdom Rush throws at the player to the potential surprise of anybody who has played other TD games. Enemies will typically manage the stats and organization to shrug off even the hard counter buildings. This means that they must be outsmarted to keep them from escaping.
Farmlands focuses on basic resource management. The strategy brought up by the game's tip is keeping your soldiers at the backside of where all of the nearby range towers cover, which allows for the range towers to consistently harass the enemies early, while simultaneously keeping your soldiers from being hit until they have to engage the enemy to keep them from escaping. This is a consistent strategy that will see usefulness for stages to come. But in order to make use of it, resource management is required. Leveling up towers, which is now allowed for a gold price, is consistently around in TD games, but KR gives it a purpose: it allows for creating a better kill zone where your soldiers are, preventing enemies from surviving as easily before being reinforced, which is how Barracks buildings can actually backfire in their usage: they only stop the baddies, but while they're doing, more baddies can come in and create an unwelcome formation.
There's only one new enemy type in the Farmlands, but it's one that's a showcase of KR's game design policies being good, only 2 levels in: the Wulves. In plenty of TD games, fast enemies are brutal because of their mobility making sure that they can zip past all your hard work just like that. Kingdom Rush provides a way to keep them under control: the soldiers will stop them from budging while they draw breath, nullifying all that mobility and additionally taking advantage of their woefully low stats. It's telling when cannons can suddenly hit Wulves repeatedly, despite their awful shot speed. Add to it that Barracks has the most cost-effective versatility of any tower in the game and sure enough, the game checks speed enemies.
It's a common flaw in games to make speed checks underwhelming. This can be because general attack power is too high, defense power fails to do anything useful, evasion makes the (ab)user too hard to catch, any number of factors, but there's a common problem: Game Breakers typically abuse speed, and often times it's general issues that end up deserving blame. Kingdom Rush avoids this, instead making sure that fast enemies that aren't stopped for long enough by Barracks are higher tier enemies.
As a note, bringing back the comparison to the Ice Tower in Bloons Tower Defense 5, soldiers stop the fast enemies on the spot and keeps them from moving for a while, while the Ice Tower can only do it for a second and has to wait to reload before continuing the stopping process.
This is still a training level, but it does have one critical warning flag: Wave 7 has a well-gathered group of Orcs. This group is easily wasted by a saved Rain of Fire charge, but the fact that you would want to save Rain of Fire to deal with a bunch of guys with only Low armor should be an alert: enemies will be more organized, and you can expect to see ones with more sophisticated armor than what Orcs have while simultaneously being able to shrug off Rain of Fire.
Well, unless you use star upgrades. I'll elaborate later on why I'll be using the No Star challenge as the standard for this whole thing, but the short summary is that Blazing Earth is only 6 Stars...yeah.
Level 3: Pagras
If Farmlands focused on resource management, Pagras teaches you to review the terrain. Some strategic points like Barracks, some prefer Mage Guilds and Archer Towers, some want cannons, you get the idea. There's also 2 paths the enemies can come in from to make it harder to manage early defenses, though a few strategic points covers both of them.
You'll want to position wisely, because you actually need whatever money you save by doing so to start using leveled up towers now in order to deal with the 2 new enemy types. Both of them demand that you have upgraded towers, or they will need much less effort to break through.
The first is the Shaman. In addition to more HP than Orcs, although lacking armor, Shamans have the ability to cast a spell that heals both themselves and any nearby allies for a currently considerable amount. Even Goblins are more threatening because you don't need to just kill them, you need to do so fast or the Shamans will fully heal them. Leveled up towers wll kill those enemies faster and allow you to catch Shamans exposed. Make sure you do hit the Shamans with archers and cannons, however, because the Shamans also have Magic DEF, preventing mages from being useful in pounding them to paste. This will be covered later on too.
Micromanagement also becomes more critical. Soldiers can instead be used to keep the Shamans from going near the frontliners, but this comes at the cost that the frontliners will not be stopped themselves. It's a tactical decision: do you slow down the Shamans and halt their healing; or do you keep the frontliners from getting through buying your range towers more time to do their job? Choose wisely and have no regrets.
The second new enemy type is the Ogre. Boasting 800 HPs, though again with no armor, along with 40-60 ATK, the Ogre is one mean customer. You simply need leveled archers and mages for the DPS (Damage Per Second) needed to tear through that immense amount of health, or else even with optimized micromanagement to stop any Shamans and other enemies capable of getting in the way of your other towers, you're simply not killing the Ogre, despite the fact that the Ogre is painfully slow.
Both the lack of speed and the high ATK are reasons why you don't want to stagger the Ogre, by the way. If you haven't noticed, your soldiers have HP values, which have been going down slowly so far, but now, we have an enemy that will smash them hard with that hulking club it swings like it was some Wiimote. Your soldiers from the Barracks do respawn, but it takes 10 seconds that the enemies can take advantage of to slip by. That's another factor: letting your soldiers die unnecessarily will hurt your momentum. Soldiers do, however, recover HP gradually if they're outside battle for long, but only then.
The Ogre's intent is to make sure that you are able to work without relying too much on cannons or Rain of Fire, which simply do not do much against it due to all that HP. It instead tests you on how well you're building around your archers and mages so that you can get the DPS rolling. It's a reason to avoid using cannons unnecessarily, so as to determine how well you can deal with groups without relying too much on cannons or soldiers. This is what the durable enemies will do frequently: they test you on how well you're grasping the game. The less you rely on one thing, the more havoc you can cause to enemies that shrug it off. This is a lesson that is going to pay off to learn repeatedly too.
Level 4: Twin River Pass
The game now lets you use level 3 towers. There is one problem, however: the path splits in two very early, and the 2 resulting paths both converges only at the very end while being far apart from each other that only the chokepoint strategic points cover against anything on them. This means that money has to be spent between the 2 paths. Upgrading to level 3 towers early on is a bad idea as a result. In fact, you should be able to see by this point that you will want all 4 basic types of towers covering both paths: Barracks to prevent the escape of fast enemies such as Wulves; Mage Guilds to jinx sturdy nuisances such as Orcs; cannons to blast the likes of Goblin hordes to bits; and Archer Towers to get rid of the vulnerable enemies such as Shamans.
This will go through your funds fast, so you especially want to make sure your early defenses are functioning, as it will buy time to clean up anything that does start escaping. Still, you will want efficient kill zones, because of the new enemy types. The Bandits have good mobility and additionally have good enough ATK to tear through soldiers who try to hold them in place. They don't have much durability or anything in the way of armor, so archer and mage fire will take them out, but having Bandits reach your emplaced soldiers can become an ugly proposition, as the Bandits can even dodge melee attacks. (Wulves can too, but it's a lower chance and additionally much less relevant.)
Because of this, soldiers lose a lot of reliability, so you end up wanting leveled attack towers to be able to kill enemies with natural attack power. If you do need to hold enemies such as Bandits for extended periods, that's generally why you'd want to upgrade Barracks buildings: simply for the improved durability, as well as a minor attack power boost if that suits your fancy. Brigands, the other new enemy type, are demanding of leveled soldier usage. They don't have the attack power that Bandits--or any future enemies for that matter--do have, but they have one aspect that makes them not easy: armor that amounts to 50% DEF. This means that mages are a must to deal with them, and even then, mages fire slowly. This in combination with the Brigands' still decent HP means that Brigands still have to be stopped by soldiers to prevent them from escaping the mage's shots.
Surprisingly, though, the game uses the Brigands' yellow box advice to instead teach about a different aspect: cannons ignoring half the armor rating. This means that they are able to damage armor guys such as the Brigands more consistently, though not fully. It wasn't noteworthy earlier because Orcs had only 30% DEF armor, so cannons dealt only about +20% extra of what they'd be dealing without this trait, which is anything but impressive with their stats. The Brigands' 50% DEF means that they take half damage from archer and soldier attacks, but cannons deal 75% instead of 50%. That's pretty handy, and it helps that the Brigands don't have too much HP. The balance is art here too: cannons are expensive because splash shouldn't be spammable and neither should anti-armor; and then they fire slow to keep splash from managing DPS and anti-armor from being powerful, and they have low attack power too to prevent the splash from being strong and the anti-armor from being too brutal. However, as you see, both the splash and the anti-armor each justify being checked by all 3 weaknesses. So all of these traits clash with each other, and the fact that a 2 strength, 3 weakness tower type is still stellar because it can have its usefulness jump because of a key mechanic is a testament to Kingdom Rush's inherently good design.
The partial-ignore armor mechanic is worth talking about as a very useful concept for other games. It provides a happy medium where certain attacks still deal damage through the targeted stat, without making that same stat useless. This is good because defensive power actually does need to be kept under control, and partial-ignoring does it in a creative way. Additionally, it has the side effect of making defense power as either a division factor or a subtraction-from-multiplier factor (the latter of which KR uses) more versatile, by giving anti-armor attacks a way out of being gimped by an awful multiplier when making sure that the stuff that doesn't deserve to be good for wrecking armor actually does get shortchanged by defensive power.
Level 5: Silveroak Forest Outpost
Silveroak Forest Outpost is one of the easiest levels in the game, as it gives you a Sharpshooter Tower (Level 3 Archer Tower) right off the bat, in addition to the ability to repair a building called the Sylvan Elf Hall so that you can hire elven guys who have Sword And Bow In Accord going on. The elven guys don't come cheap and they don't even respawn if they do die, but they are adept enough to tear through enemies in general with their archery. Additionally, partway through the level, you'll get to upgrade a Sharpshooter like the one you start with to the Rangers Hideout, the fastest firing tower in the game. Needless to say, this level isn't terribly hard, but then again, every game needs its Breather Level.
And Kingdom Rush incorporates the idea of involving its own Breather Level in the game's flow. At this point, you may still be overwhelmed by all the concepts involved, and there are still new concepts coming in, but right now, the game just throws highwaymen at you that you know how to deal with. Though there will be spiders that come in from the east, thankfully, it's telegraphed by their entry point being a dark forest. Good thing too, because spiders resist magic heavily. Giant Spiders are also fast, while Spider Matriarchs can spawn hatchlings who are fast enough that having no soldiers controlling the exit is a good way to lose lives fast. The Giant Spiders have paltry bounties, higher only than that of a very few enemies, and the Hatchlings do not provide any funds as a measure to prevent any late defenses abuse for grinding, so you have to worry about swarming you need consistent defenses such as a good cannon zone for. Talk about a subversion of Money Spider.
Worgs also appear, as stronger versions of Wulves who resist magic and have about equal combat power to Knights (120 HPs and net average 10 ATK, against the Knights' 150 HPs and net average 8 ATK) in addition to the dodge rate, but luckily, the Sharpshooter and Sylvan Elves are around to shower them. A player can easily take their time figuring out how to deal with them in general without problem.
At the moment, let's talk about the different tech levels. At the value tower level, there's the Sharpshooter Tower (L3 Archer Tower), the Adept Tower (L2 Mage Guild), the Dwarven Bombard (L1 Artillery Tower), and the Footmen Barracks (L2 Barracks). The quantity towers are the Archer and Marksman Towers (L1 and L2 Archer Towers respectively), the Mage Tower (L1 Mage Guild), and the Militia Barracks (L1 Barracks). As for the tech towers, what's currently available are the Rangers Hideout (L4 Archer Tower), the Wizard Tower (L3 Mage Guild), the Dwarven Artillery and Dwarven Howitzer (L2 and L3 Artillery Towers respectively), and the Knights Barracks (L3 Barracks). Now you might notice that the Barracks and cannon buildings are considered in this analysis to be at higher tech levels than their costs would otherwise suggest. For Barracks, this is because leveled Barracks have flow issues. The money that goes to Barracks upgrades could be going to the actual attack towers that get rid of the enemies. This isn't so bad with the Footmen Barracks, but the Knights Barracks really suffers in general. Cannons, meanwhile, rely rather strongly on splash, much as that is their job, it comes at the cost of DPS, and should consequently be treated as a leveled tower so that it isn't teched unnecessarily.
What you'd want to do in general is have plenty of value towers, use some leftover funds on quantity towers, and focus on a few tech towers that devastate whoever you really detest. Yeah, really basic strategy. Also, it should be noted that Level 4 towers can get special abilities that can do different things. The Rangers Hideout, for example, can get Poison Arrows to poison enemies with their shots, or hire a druid who will summon tree roots that will wrap around enemies and trap and crush them momentarily.
Of course, Silveroak Forest doesn't finish off without introducing one last new enemy type: the Marauder. With 60% DEF and 600 HPs, the Marauder is brutal to any setup that doesn't bother with enough funding for soldiers and mages. It is by sheer mercy that the only 2 Marauders on the stage appear on the last wave where they're easily thwarted by all the defenses you'd have. However, in later levels, you won't have that luxury.
Level 6: The Citadel
Hopefully, you'd be rested up by now, because your forces are now at the capital of Linirea, so you can expect an important, fierce battle to take place, just for more reason why Silveroak is a Breather Level. Luckily, you do have 7 NPC guys helping you, in the form of Paladins who have good stats, though they don't have a range attack, and they additionally do not respawn at all. This is to replicate that the enemy force will be outright merciless enough to potentially push you back gradually.
Before we can get to the new towers, there's a new factor in the level: flying enemies, in the form of Gargoyles. Flying enemies will fly along the path, and though they have only standard at best stats, they can't be blocked by soldiers at all. Cannons also can't target them, and instead can only damage them with splash from attacks targeting other nearby enemies. This means that if you've been somehow getting by spamming those two types of buildings, no chance you'll get any further. This ensures that you have to provide funds toward archer and mage towers, which can't manage clump punishment.
With that out of the way, The Citadel introduces two new buildings: the Arcane Wizard tower and the Holy Order. Both are still stronger versions of their earlier versions, but you may notice that both towers have weaknesses in comparison to their counterparts, namely that the Arcane Wizard has a slower reload rate than the regular Wizard, and the Holy Order's Paladins take 4 additional seconds to respawn. This is actually a good game design method: allowing much stronger versions of units, but also giving them weaknesses that make sure that they can't do anything mindless enough to manage soloing. This is a design choice that even is placed on every single Level 4 building in the game, at least more or less.
The Holy Order is more balance art, by the way. There are games like Super Smash Bros. and Kid Icarus Uprising that think that a very strong on-balance strength is balanced well by an off-balance weakness. This is generally a mistake, and certainly one that is made in those two games, because in order for the off-balance weakness to matter, the guy with it would have to be outplayed enough, which they can make harder with that on-balance strength. Here, Kingdom Rush avoids making that horrible mistake: though the off-balance weakness of the Holy Order only matters if a given Paladin is dead, the on-balance strength of the Holy Order is only really useful if the Paladins are being hit, which too much of will still kill them. That's how you balance this sort of thing: making sure that the strength only works in a way that allows the weakness to potentially kick in. SSB fails miserably by doing things like giving Olimar obscene melee range in a game with unconditional flinching problems and then making his weakness terrible survivability when somebody can get past that melee range. KIU is also stupid enough to make an indefinite buff that about doubles attack power require hitting the user, which is made obscene when even Mega Laser is given problems doing so by excessive mobility.
The Arcane Wizard is pretty standard fare, though it comes with some pleasant benefits. First, it hits targets immediately upon attacking. This prevents misses that would waste the damage the Arcane Wizard would fail to do otherwise, which is good because it's already a Mighty Glacier. Second, the base damage values, though weakened because of calculations (more or less, one value is used and divided between 10 hits, but the game truncates damage for each hit too), are nevertheless very good so they can still hit their first target for heavy immediate damage. Third, Arcane Wizards have access to Death Ray for instant death to an enemy every now and then, and Teleport to move enemies back along the path.
To get this out of the way, there is one L4 tower that actually doesn't have a non-cost weakness for teching from its L3 counterpart: the Rangers Hideout. This is because the Rangers Hideout already has a significant weakness: it has trouble hurting armor enemies. It is actually common for armor enemies to be at the forefront of a wave taking the shots, which means that the Rangers Hideout is generally wasted on those waves because it's not targeting anything behind them. This can be fixed by Poison Arrows, as the Rangers will start shooting different enemies to make sure to poison more of them, thus catching protected enemies more easily, but there's two weaknesses created by that: first is that the arrows will not focus on one enemy when it could be needed; and second is that certain enemies (constructs and spiders) are immune to poison and thus will additionally not be targeted if there's anything that isn't immune in range.
Now I just mentioned that there could be a need to catch enemies behind armor guys. Well, the Shadow Archers provide that need. As their name implies, they are range attackers, who actually have decent HP and (a little) Magic DEF. More importantly, as soon as one of your soldiers is within their range, the Shadow Archers will start shooting away, so you will want to Rally them to maneuver your guys with that in mind. Keep in mind that they will not engage in Mook Chivalry, so if more Shadow Archers are capable of firing at the same guy, they will, and it will cause their otherwise mediocre ATK to get effectively multiplied by a considerable number. They will, however, stop to shoot at anybody they can starting with anybody further from the exit, even if those targets are behind them just sitting there looking pretty. Still, at the end of the day, they're often behind armor guys, so creativity would be a boon to either wipe out the armor force efficiently or cripple the archers' ability to cause problems.
Speaking of armor guys, the Dark Knights are the more sophisticated armor guys I promised about. They may have half as much health as Marauders, but they have 80% DEF, they're faster, and they're more able to come in groups. Although more than Mage Guilds can actually hurt Dark Knights, Dark Knights themselves are capable of being all-around threats, continuing with the comparisons to their light counterparts, the Paladins, who can make use of special abilities to increase their defenses and rip through groups and armor guys.
Kingdom Rush involves a threatening baddie type who shows up at the end of certain levels: bosses. Each boss has no Physical or Magic DEF and is also slow in general, but they have a boatload of HP, take off all of the player's lives instantly if they escape, and spawn mooks continuously to keep your defenses at every location busy. Additionally, they have immunity to instant death and special abilities that affect movement, either one of which would be cheap, but that doesn't mean the special abilities involved are entirely useless, since they can still be used on the minions. The Juggernaut doesn't have much going for him beyond being a construct while his minions, unique to his fight, can be spawned anywhere on the map that isn't past the 3 Imperial Guards at the top, with decent stats going for them. He has one particular key problem: well-upgraded Paladins can put him in a melee lock loop. The Juggernaut does have an area attack, but it doesn't do enough damage to wreck the Paladins a bit faster. This isn't too bad, though, because he's the first boss. He's supposed to be a little easy, though still there to make sure that you understand how vital it is to tear through enemies' HP.
Level 7: Coldstep Mines
Saving the capital of some country from attack is something that wouldn't be left unrewarded, and sure enough, you get support from the king's Musketeers, which means a new tower: the Musketeer Garrison, an alternate L4 Archer tower. On paper, this doesn't seem like much, because the Musketeers fire as slow as standard mages do, and this comes out of the Sharpshooter Tower as well, but they do have the best range in the game. While that can actually backfire by having Musketeers shoot guys they shouldn't, that only means that Musketeers have a significant range advantage. It doesn't seem like a huge advantage when the Rangers Hideout has Great range, but if you place them on any strategic point next to the one that a standard 180 degree turn goes right around, the Musketeers will cover the turn itself. There's 3 such turns on the map. Not only that, but there are building points from where a Musketeer's range can easily tip on significant locations, making sure that it doesn't occupy spaces that could be handled by other towers. Add to it the nice base damage and they have an advantage in immediate damage. (Author's note: I should also point out that I'd be for Musketeers having an armor half-ignore feature. They seriously need it since they're terrible flood control regardless. It's not like they don't deserve it when they have rather fly damage bases. It seriously sucks to have them crippled so easily.)
To make sure that positioning isn't forced, Musketeers have Sniper Shot for another instant death ability, one that is less expensive than Death Ray at that, and has better range too, but suffers from having limited success chance, though there is consolation damage on failure; and Shrapnel Shot, for blasting groups into bits every now and then. Neither is perfect, but both abilities, especially Shrapnel Shot, are there to keep the Musketeers from being too confined to certain locations.
This, by the way, points out that an L4 tower's special abilities have their usefulness vary depending on the tower's own position. Poison Arrows, Holy Strike, and Death Ray, for example, are better earlier into the path where it's easier to catch certain enemies and weaken new ones, while you want Wrath of the Forest, Shield of Valor, and Teleport on exit guards to keep enemies from getting through at the last second.
There's a concept that needs to be brought up: Dungeon Bypass. Coldstep Mines uses it by having mine tunnels that enemies can go through, keeping them safe from your towers. This means that you want defenses both by the entry point and by the exit, because those are the 2/4 (this makes sense in context) of the path are NOT bypassed, but don't be afraid to have protection covering the middle 2/4, simply to reduce the number of enemies that get near the exit. Also, the Dungeon Bypass makes Musketeers more handy by giving them more immediate damage opportunities as long as they're covering the exits.
There's two new types of enemies. First up is Trolls in the mountains, thought you ought to know. These guys are not only rough and tough, they additionally recover health slowly but surely. This means that you want leveled DPS towers going. I need to point out that Mage Guilds, despite firing slower, actually have better DPS values than Archer Towers do. Yep, there's actually a reason to use Mage Guilds not just to wreck armor guys, but in general: simply to put the continual hurt on baddies. It's not even the Troll's regen that encourages this in and of itself, though it certainly contributes. It's the Barracks mechanic in and of itself, stopping those baddies and thus multiplying the DPS influence. Okay, so the armor counter has problems doing its job, but then it's able to work against other threats. This is good game design: making a counter viable by allowing it to do more than the countering. This doubly encourages affinity since it's generally key to handling armor busters properly.
The other introduced enemy type in Coldstep Mines is the Winter Wolves. They have sufficient combat stats to outpace Paladins, they still have the good ol' wolf speed, and they have Magic DEF. These guys make it tempting for you to tech your archer towers, but this brings up another good thing about Kingdom Rush: every single enemy type with Magic DEF can be IDed to working effect. If you haven't noticed, all the enemies that do have Magic DEF have different traits, different strengths, and different weaknesses. Spiders could be blasted apart by cannons. Shamans could be isolated or overwhelmed. Shadow Archers are innate backliners and additionally could be tricked into firing at guys they shouldn't bother with. And wolves could be stopped completely by soldiers while having faulty attack power ratings. Winter Wolves still demand you to upgrade, because 30 average ATK isn't pleasant, but if you played your cards right, you could manage the common pattern of what happens with the IDing: you could keep the level of your archer towers low. This would save you money that could go to the towers you could use to hope to rip through enemy armor like it was tin foil. Winter Wolves even have a high bounty for taking off 1 life, which brings up another KR mechanic: if an enemy escapes, you still get the Gold for that enemy, but you still lose the number of lives according to its penalty. Winter Wolves have the highest Bounty/Penalty ratio of any non-premium enemy at 35/1 = 35. The game basically is being liberal to anybody who lets a Winter Wolf escape either by inability or choice, simply because Winter Wolves do still demand archer towers.
In essence, how low you can have your archer levels in relation to the stage's difficulty generally reflected on your skill in KR. A Musketeer Garrison isn't all that bad to have, as positioning it well still rewards you, but this sort of stuff never gets more pronounced than it does in the next stage.
Level 8: Icewind Pass
Kingdom Rush may have an Excuse Plot, but never let it be said that it isn't aware of its own design, because Icewind Pass is indeed that brutal halfway point that makes you wonder if the good guys can ever win, even if by all rights they would. It's what makes movies like Star Wars The Empire Strikes Back and Back to the Future Part II memorable, granted when they don't rely on certain spoilers everybody knows as in the case of the former but those certainly help my point about ESB when Star Wars works with metaphysical aspects to begin with. And Icewind Pass just so happens to be my favorite level in the game.
How the level works is that most enemies will come from the north, but spiders exclusively will come from the south. As you see, spiders are back, so cannons sound good, but then the game throws you a curve ball if you decide to rely on them: it continuously throws Trolls, Gargoyles, Shadow Archers, and Winter Wolves right at you. All of these have the HP to shrug off cannons, and the latter two have Magic DEF to additionally discourage mages. Troll Champions, new enemies who throw armor-ignoring axes from afar (yep, ranged anti-armor), even have a lot of HP.
This common weakness to archery among all the sent enemies makes it very tempting to tech your archer towers. But you must persevere. All of these enemies can be beaten without leveling up archers much by simply outsmarting them. Even the Winter Wolves aren't invincible to cannons, they're just armed with plenty of HP to resist. They have all-around threatening stats to be sure, but they don't have anything impressive enough to completely wreck a well-oiled soldier zone. Keeping your archer level low lets you save up your money for armor buster towers.
Wave 12, which I nickname the Dark Knight March, is what really puts your tower setup to the test. Consisting of 18 Dark Knights and 12 Shadow Archers, it's the level's climax, and the best point of the game's level design. If you have been relying too much on archer towers all this time, they will end up shooting at the Dark Knights for minimized damage, and even if they could hit the Shadow Archers, the Dark Knights are still virtually unscathed. Nobody wants a Dark Knight count in the double digits anywhere near the exit, so it's a must that some of them must be dealt with quickly. The result is that anti-armor of plentiful variety must be covering every part of the path, because no single form of anti-armor can hope to solo even half of the black-armored blackhearts. And not only must your tower setup be good enough, so must your micromanagement to keep the Shadow Archers under control, because you still need soldiers who don't get showered by arrows in order to keep the Dark Knights from escaping your armor busters.
This is what is so good about armor: it encourages anti-armor methods, which themselves require actual skill to control to any welcome degree, which in turn encourages player synergy. This is what can be deciphered within, ironically, Super Smash Bros., which turns out to have a mode with an objective that actually does succeed in encouraging genuine creativity this way: KO records in 15 Minute Melee/Brawl. Getting the fast KOs needed to make new Wireframes spawn faster means that you have to leave yourself in danger trying to use an armor busting attack, but that's where creativity and synergy protects you. Don't understand about Mr. G&W's Glass Cannon status? Remember that he's from arcade-style games. Want to prove that Link is cool? Well, good news: he's the game's variety savant, which helps against move staling. Interested in overcoming Zelda's terrible defenses? She's the bearer of the Triforce of Wisdom for a reason. Like using Pichu like some Killer Rabbit? Well, what doesn't kill you only makes you stronger. See the sort of depth that SSB went for, and ended up ruining by commiting to stupid decisions like unconditional flinching in multiplayer? But the point is still there: good, strong defensive power improves the variety by encouraging affinity to let its counters work, among other reasons.
Not only that, but as we see, it punishes overzealous usage of speed options. Here's some good design: minimizing the necessity of the speed option AND testing players for creative trap setting. In Kingdom Rush's case, all enemies with Magic DEF can be dealt with in more ways than simple archer fire, while armor guys just laugh at archer fire AND require that your towers are working together well to cover all bases. This makes sure that the likes of mages and cannons are really worth considering.
The clincher? Defensive power, within reasonably beatable levels, NEVER runs the risk of making anything useless, simply because its blind spot is being useless unless the unit gets hit and, by very simple definition at least, punished for it. Obviously, here, it has brought up a good design policy. And this isn't the last time it does that in this game's Campaign levels either. But that's a subject for another time.
Since you may be thinking that Dark Knight March isn't the big deal I make it out to be, it's actually the biggest reason why I use the No Star Challenge as the standard. With so much as Scorched Earth for only 2 Stars, it's an afterthought. Just drop meteors on the front Dark Knights and watch them and quite a few Shadow archers fry, making it insultingly easy to kill the remaining guys with their numbers severely cut. You have no such luck in the No Star Challenge, because Rain of Fire will not even kill any Shadow Archers it hits, let alone any Dark Knights. Oh, it will do some damage, but because you have only one charge, it causes nowhere near as much havoc on the Dark Knight March.
Once Wave 12 is dealt with, the level is a good deal more freeform, which provides for some free exploration room. A feature exclusive to this stage is the ice cave where, once you break it open with Rain of Fire, you can hire a Sasquatch for 500G. This actually brings up a design flaw: even though the Sasquatch has a whopping 2500 HPs, he can still die from excessive abuse and additionally doesn't respawn, which means that you'd have to pay another 500G to rehire him. This would be okay, if the game didn't decide to prevent you from moving him anywhere near the exit, which would have made him well actually worth considering before Wave 18, when he'd no longer be suffering range abuse. Oh well, at least the game's ending does have Sassy around. Look for the guy who says "Grrr" among the celebration to your avatar's promotion.
There's also two new tower types in this stage: the 500mm Big Bertha for at the very least among the top 3 of the best crowd control in the game if you don't mind the firing speed issues; and the Barbarian Mead Hall for axe-wielding barbarians who have immense HP and actually working attack but no armor, and can even throw axes to potentially act as psuedo-Musketeers. Both are towers that are pretty much player flavor, though they do bring up a neat design decision: every single L4 tower except the Holy Order actually has the potential to target flying enemies. The Big Bertha and Barbarians only do so with special abilities, but even so, this means that mages and archers are not exclusively needed to deal with them the entire game. (Well, cannons can also hit flying enemies with splash damage. I'll let you, the reader, figure out how you can make use of that.) Of course, the ways to target flying enemies do cost more money that could be going to actual crowd control, so yeah.
Aside from the Troll Champion, another two enemy types premiere in this level. The Troll Chieftain, in addition to having high durability, can beat on the drum he carries to rally his nearby Troll compatriots into a warcry that hikes up their stats, most notably their mobility. Too close to the exit with decent support and he certainly becomes a nuisance. Luckily, he has lower ATK than his friends, so if he's caught alone, he's easily distracted for a while. But hey, the Troll family of enemies have managed to keep things interesting in how they work. I can't say they don't deserve some credit.
The Yeti is kind of bland, being a mega-HP baddie, but he does have one aspect going for him: area attacks. The Yeti attacks slow, but the area attacks means that a swarm of soldiers will not stall it by forcing it to attack each of them one at a time while they keep respawning. He pounds at them to hit them all at once and will inevitably go on his merry way once they're dead. A highly upgraded Holy Order can outpace a single Yeti's damage output, but since the Yeti isn't a boss, before long, you're fighting a number of Yetis, and having multiple Yetis fight the same Holy Order will end badly for the Paladins.
These new enemies don't play much of a role quite yet, since they appear after a key wave requiring plenty of defenses, but in the next level, they actually appear when they can actually cause problems.
Level 9: Stormcloud Temple
(Before I start, I want to remark that I find this level's design to be lazy. The Excuse Plot in general isn't worth worrying about, but this level particularly involves Fridge Logic. How the heck does it take 20 minutes to complete a spell? I can buy that the spell is for an entire army, but there's still going to be plenty of backup mages handling the spell casting. Now remarking about this can seem like cheap nitpicking, but the level brings about plenty of things I actually have complaints about due to execution that falls flat.)
Gradually, the enemies have been getting more fierce, though that's to be expected. Still, the enemy setups have managed to expect some rather confining stuff. It is true that the Dark Knight March from the previous level does manage to be set up to demand considerable mage and cannon usage, but the game still has some puzzle element to it, with towers like the Rangers Hideout being but a piece of the puzzle as a simple support tower, and we still haven't reached the apex of the game's difficulty yet.
The Sorerer Mage transforms the gameplay. What he does is provide a Curse debuff to any enemy he hits, causing them for the debuff's duration to take gradual damage and a halved armor rating. The halved armor rating is the big deal, because it allows towers like the Rangers Hideout to actually hurt armor enemies, allowing them to work as their own sorts of characters, so to speak, to build around, rather than simple members of an army. The early parts are still a puzzle of sorts, but there's not a lot that can be done about it.
Now note that I basically said that each L4 tower type is capable of working as a character to build around. Here's the big blindspots of each L4 tower type individually:
*Holy Order: fliers and 1HKs (general anti-armor and range enemies can also be a nuisance but are plausible to ID to working effect)
*Barbarian Mead Hall: heavy pressure
*Rangers Hideout: armor guys
*Musketeer Garrison: floods
*Arcane Wizard: thick groups
*Sorcerer Mage: resilient guys
*Big Bertha: fast enemies
*???: durable groups
This means that you'd want other towers to neutralize the blindspot enemies. That's the basic concept of the Sorcerer Mage tower: teamwork. It hits an enemy to debuff them and then that Rangers Hideout just ahead can actually shoot them. The character aspect is simply the meta concept.
(Author's Note: I have to note that I find the Sorcerer Mage to be OP. It has better DPS than the Arcane Wizard with no real disadvantage, and the Golem is an incredibly powerful road unit that doesn't even get gimped by area attacking while having one of its own. I would find that the Sorcerer Mage's BD should be nerfed 42-78 to 31-57 to decrease the DPS considerably, and have the Golem take 16 seconds respawn instead of only 8.)
If you don't think I know what I'm talking about, Dark Slayers will gladly prove you wrong. Each one packs 1200 HPs AND 95% DEF. If your mages are not leveled enough, he WILL punch through. He simply has too much HP for cannons, and that 95% DEF means that unless he's Cursed, Rangers Hideouts won't even make a dent without special abilities. Dark Slayers even resist poison for good measure, making sure that it has to be prolonged beyond the initial 3 second limit to do any damage. However, even he will fall if he takes too much abuse, and that's still solved by making sure that your anti-armor is linked well enough that he can't do whatever is the AI equivalent of IDing in order to escape one form of it because he will just be fighting off another one. Games are supposed to be about creativity, right?
The other new enemy type, the Rocket Rider, does manage to annoy a lot of people, reason being is because they're the most brutal flying enemy type in the game. Not only do they have nearly 4 times as much durability as a Gargoyle without even being slower, but they have a special ability: Turbo. It activates only once, but it's enough to cause a lot of problems because it's an immense speed jump that has the Rocket Rider move very fast through a given area. It even triggers the moment the Rider is hit, and no sooner, which means that you better have something covering the early parts to hit them or they will still have their Turbo approaching the end of the path. But that's not going to be enough. You additionally need to hit them for heavy damage as fast as you can. This ends up making Musketeers useful because they have both the range and the base damage to manage this, and additionally keep the Rocket Riders harassed so that they can manage that one last shot needed to finish them.
With these new durable enemies, in addition to the actually threatening Troll Chieftains and doubly threatening Yetis, there's a focus on the advanced archers and mages. That's not to say that cannons or soldiers are useless, but both the Big Bertha and the Holy Order will no doubt struggle to find any semblance of usefulness in this level. Especially when J.T. comes into the picture and....he's surprisingly easy to isolate due to limited mooks, while having an actual instant kill attack that even covers an area, so it instantly gimps a Holy Order.
Well, at least J.T. has an answer to Holy Order spam. Would have been nice if it avoided an extreme though.
Level 10: The Valardul Wastes
Stormcloud Temple had a focus on mage and archer towers, and consequently focused on individual targets. This ended up coming at the cost that cannon upgrades would just sit there collecting dust. It's one of KR's less likeable design decisions, but it does at least build up the tension for introducing the final tower of the game: the Tesla x104.
What the Tesla x104 does is that it fires a lightning bolt at a given enemy, then the bolt will make an attempt to chain to another enemy within its own range, and repeat until it hits as many enemies as allowed, a base of 3 and a maximum of 5 with Supercharged Bolt 2. The lightning bolt, of course, hits the enemies for focused damage, though the second and subsequent enemies take less. What helps is that Tesla even attacks faster than other artillery towers. Of course, if you haven't noticed, it hits a limited number of enemies, so teching to it becomes a dangerous decision when the Dwarven Howitzer is already solid group control, but Tesla has a fix for that which doubles as its bread-and-butter setup cornerstone: Overcharge. Overcharge, once it is readied by buying the upgrade, triggers every single time Tesla attacks and hits EVERY enemy within Tesla's range for some minor True Damage. If Tesla is positioned properly, there is absolutely no enemy in the game that can move through its range in its time between attacks. This means that Overcharge works as a health toll, and a handy one at that, not only catching enemies who rely on speed, such as Wulves, but additionally makes enemies' health values a more important factor.
Even though the Tesla has weaknesses outside cost, it's still rather powerful. Of course, since we're having the fight within enemy territory now, cost needs to become a weakness. The game provides a way to exploit that: Demon enemies. Though slower than non-demon counterparts, not only are they too durable for cannons, they have 60% Magic DEF and an ability called Infernal Combusion, where as soon as they die, they blow up causing an area attack that hits hard. Spawns are almost equivalent to Trolls (though lack their Regen and have lower ATK, but Trolls themselves didn't have Magic DEF), Hounds are an easy comparison to Winter Wolves (right down to even having the same dodge rates, which the game doesn't tell you), and Lords are basically Troll Chieftains, though instead of giving the minions all stat buffs simply provides shields which have no chance of backfiring.
The single blindspot to general Demon stat setups is archer towers, because those are unaffected by both the explosions and the Magic DEF, and can actually hurt the nuisances. Though don't be afraid to throw in some soldier blocking. Remember: Demon Spawns still have worse ATK than Trolls and their explosions only trigger when they die; Demon Hounds are still slower than Winter Wolves so if they kill early soldiers it won't be as punishing; and Demon Lords you'd want to isolate as best you can anyway so that they don't provide so many shields. Additionally, soldiers can still stagger enemies such as Brigands and Wolves.
There's two pleasant results of this. First is that upgrading archer towers actually becomes useful. This especially applies with the Rangers Hideout, which has been suffering redundancy issues. Now that extra oomph can actually be useful. It still serves the same purpose in the game's balance (a speed-overfocus trap) but now it actually has flow. You still want other things to handle the armor enemies and thick groups because, yes, they are still inbound.
The second one is the relationship with the Tesla x104. Demons are both the bane of the Tesla's existence, and the playthings of it. How is this possible? Well, because you need archers to kill the demons, you need to spend money on them, and then you still have to provide expenses for the mages and soldiers needed to stop the armor baddies as well. After that, you have only a little money left when cannons are expensive and provide little benefit. And yet if you can get the Tesla rolling through all this trouble without losing momentum, you most certainly earn its benefits. And what benefits they are, because the front Demon Spawn suffers a guaranteed 3HK against the Overcharge 2 setup, the next one is likely to die another hit later, and then the third one gets KOed yet another hit later. This is likely to happen because Overcharge competes with Big Bertha's Cluster Bombs Xtreme for best crowd control in the game, and Tesla even hits flying enemies, making it VERY handy against Rocket Riders, which means Tesla ultimately has consistent flow.
If you didn't get all that, Demon enemies' relationship with the Tesla x104 is every bit as interesting as Meta Knight's general design as a Wake Up Call Character. And don't even claim that the latter isn't interesting, because it is. The only worry is that they can feel gimmicky, but they will prove otherwise in the final level.
There's also a gimmick to worry about in the level, but it's more to get cannons to have some flow in this level. The Graveyard spawns a Skeleton every time a humanoid baddie dies. Skeletons are even slower than the demon enemies and don't have a lot of HP, but the Graveyard is late into the path so it requires some good late defenses to intercept. Also, just in case you think you're safe because of the Tesla x104, though, any humanoid baddie with at least 300 Max HP has their death spawn a Skeleton KNIGHT, who as you may guess is vastly tougher and even has an actual DEF stat. Also keep in mind that the Skeletons have painfully bad Bounties.
(Author's Note: I'd be for revamping the regular Skeleton to trade a little HP for a little DEF so that they encourage mages, and nerfing the Skeleton Knights outright. The Skeleton Knights are ridiculous as is, and they're even more sadistic on Hard Mode because Demon Spawns have their Max HP increased from 250 to the magic number of 300.)
Naturally, that brings up the Tesla x104's major flaw: it lacks the punch to deal with a considerable durable enemy headcount. Overcharge deals only so much damage, and the lightning bolt can't possibly cover all of them. Add to it that Tesla can't get a special ability for anything else and soon enough, you will start considering the 500mm Big Bertha to start clearing up the clutter. If you don't, the game has a VERY heavy amount of Dark Knights and Demons waiting for you.
Showing once again thatthe game is aware of its own design.
Level 11: (God) Forsaken Valley
You may have caught on that in general, armor enemies have been moving down one path while the monster baddies have been moving down the other. And this level seems to apply it in spades. Well, you'll be in for a surprise. But let's talk about the one new baddie introduced in this level that isn't a copy-and-paste one: the Necromancer. (The Demon Imp is really the halfway point between the Gargoyle and Rocket Rider, and the Magma Elemental is a Mighty Glacier version of the Yeti.)
This guy is mercifully introduced not so quickly, because he's basically a Boss In Mook's Clothing, so wouldn't it be annoying if he appeared in Wave 1, because you'd have to dedicate your entire defense to dealing with him, and by the way, you start with 1300G, so say hi to Suspicious Videogame Generousity. Anyway, the Necromancer is a guy who casts spells and doesn't seem like much when you have dealt with Troll Champions, until you realize that he can summon a bunch of Skeletons, sometimes throwing SKELETON KNIGHTS into the mix. You can see that the sooner he dies, the better. You need soldiers to engage him in melee because he can do his fell summoning at any point he wants otherwise, including right after a range attack, just so that the skeletons are getting stopped only by severely weakened soldiers. Not only that, but you need cannons to destroy the skeletons and DPS towers to wreck the Necromancer and any other baddies who try to support the Skeletons. Oh, and speaking of the Necromancer's Skeletons, they do NOT provide any Gold, unlike Graveyard ones which do that. So trying to grind off of the Necromancer isn't going to work, even if you could let more Skeletons spawn without losing momentum. May as well just kill the vile wizard, which is hard enough.
The level has a big secret to everybody: it demands budgeting and risktaking via early calls. You must make sure that your towers are mopping up enemies as efficiently as possible, which requires a fine balance between tempo and cost-effectiveness, and then make sure you can call enemies earlier for the funds you are going to need for considering things other than mages on the right, archers on the left. This doesn't seem like a big deal, and Wave 17 certainly throws a downright brutal Demon swarm attack. But then Wave 18 has an unpleasant surprise for anybody who decided to spam DPS towers on respective paths: it sends SPIDERS ON THE RIGHT, ARMOR GUYS ON THE LEFT. And yes, there's even a *DARK SLAYER* on the left.
This means that you want to not only have things like cannons and special abilities in order to have things on both paths that are less discriminate about what they're dealing with, but make sure that they are flowing naturally in order to deal with the problems that Wave 17 causes. This makes Forsaken Valley one of the hardest levels in Campaign to figure out, simply because of how harsh it becomes even if you can manage working aggressive play, let alone that it punishes players for being too conservative or upgrade-happy. And yet when you figure it out and thus can manage to survive in enemy territory for lengthy periods, take it as a sign that you are undoubtedly awesome.
Granted, that is assuming you are doing the No Star Challenge, rather than using something like Scorching/Blazing Earth as a crutch.
Level 12: The Dark Tower
After your lengthy journey (though it can be only about 3 hours), you finally make it to the Very Definitely Final Level, taking place at Vez'nan's Supervillain Lair. Your forces have gathered right outside the tower ready to attack it, and the stakes are set: your forces have the common goal of making sure Vez'nan's own head is on a pike like what he did to others and plans to do to you, but if Vez'nan escapes, he will be free to cause calamity over Linirea for Heaven knows how long to come. The latter is actually just guessed, though easily when you consider how much damage he does to Paladins with his abuse of the Number of the Beast.
Naturally, Vez'nan is not going down without a fight. And naturally, what a fight it is. Right off the bat, you might think that 1300G will make things easy enough, especially seeing as there are no new towers or enemies, it is just you and your wits against the game, but again it is Suspicious Videogame Generousity. And you see it prove as such the moment you move the mouse icon over the enemy icons on the tower entrances. The 2 Demon Hounds actually come out right away when Wave 1 starts, forcing considerable fund expenditure on archers AND some micromanagement to keep the Bandits from getting in the way; there's a Graveyard to spawn Skeletons for the number of humanoid enemies you have to deal with; and most importantly, there's a Necromancer--yes, on Wave 1, congratulate me on Tempting Fate yet again--and he's even backed by Brigands who will gladly sponge the arrows of the archers who are needed to deal with the Demon Spawns. (As you see, the demons actually serve a sensible purpose.) And just in case you think to spam cannons hoping to just survive rather than care about NLL, Wave 2 has flying enemies including 2 Demon Imps.
This is the sort of thing you'd have to be ready for. As such, all of your skills will be put to the test. Terrain study, resource management, tower understanding, micromanagement, and creativity are ALL needed to be able to fight back. Missing even one of those is likely to, by itself, result in the Wave 1 Necromancer being able to summon 20+ Skeletons past all of your defenses. Even past the Necromancer and the Wave 2 flying enemies, there's still plenty of threats to deal with. Demon guys, armor guys, Shadow Archers, thick crowds, Rocket Riders, and even Magma Elementals and more Necromancers will do what they can to try to get through or clear the path for their allies, and they're additionally organized, the most blatant example being that armor guys like to be right in the front taking arrows for the demon guys. Vez'nan will even summon in Demon Spawns and Hounds from the summoning circles to really hinder your soldiers, in addition to locking your towers with spells. He's pulling out all the stops, and for you to win, you must do the same.
Vez'nan does, of course, come out, using his spells from before, a close range area attack that is very powerful, and an instant kill range attack that steals the souls of the victims. He doesn't seem to have too much HP, but this is reason to suspect that, yes, he has a One Winged Angel form. Granted, it's a Clipped Winged Angel form if he's nowhere near the exit because all he can do is another close range area attack, with no more access to his spells, but if he is close, the form actually has working mobility which can easily make up for all the abilities lost in the new form. This does bring up that you want to be aggressive against the bosses so that you can deal enough damage to them before they are supported too heavily by their minions.
General level design
With all 12 levels covered, what we would need to be done now is figure out the general ideas of what Kingdom Rush did. Here they are, and they actually are rather brilliant:
1) Make sure each level focuses on a common concept, especially making sure that same concept will be used in future levels. This is common sense, but you still want to avoid having random for its own sake level design like Advance Wars Days of Ruin did, or you'll risk managing Schizophrenic Difficulty.
2) Consider buildup for the next level's concept. This allows the levels to link, and by providing a problem for players to contend with, the concept of the next level will become more welcome. Conversely, the current level's concept can provide a calm before the storm that the next level's would cause. Either way, the levels flow better and become more engaging.
3) Don't be afraid to have a Breather Level. Preferably, have it compliment the pace so that it manages to be welcome. This ensures that the players don't end up discouraged trying to figure out how your game works, and make sure they can get ready for what's to come.
4) Introduce the most unique characters (or towers in KR's case) later than anything else. While unique aspects should be made use of in the early game, saving some of them for later on both maintains the game's challenge and reduces the risk of burnout. You want to encourage players to consider other characters in the lategame instead of sticking with who they have been working with this whole time barring strong enough preference. (This is probably why the Sorcerer Mage and Tesla x104 are introduced last.)
5) On that note, also make sure that armored enemies are set up to test the player's ability to organize, and only provide any really versatile anti-armor that lets any character hurt armor guys (in KR's case, the Sorcerer Mage) when the player can be trusted to understand the reason for their existence. It is okay for the armored baddies to lose their Hero Killer status as long as their threat value remains at least mid-tier right to the end of the game.
In closing, Kingdom Rush manages some excellent level design, at least for the regular Campaign. I'm not sure about the challenges or the Premium stages, because both of them seem to encourage the star upgrades to death. Still, Kingdom Rush provides plenty to learn about level design, more than what I can say about a game like Kid Icarus Uprising, which has levels being disorganized and bland in the name of overfocus on gimmicks, with insufficient care about balance to rub salt on the wound. Game designers can take note of the ideas to provide for their own game, and ultimately benefit the gaming world by setting up a creativity standard like Kingdom Rush did.