9 min read

pixel park zombie - Game design document

The game design doc for our latest WIP game Pixel Park Zombie Run.

In the interest of community and education We would like to share with you the game design document we wrote up when big fire games started development of our forthcoming game - pixel park zombie runner.

1 Introduction.
This document specifies a design for the game play of the forthcoming Android game entitled ‘Pixel park zombie runner.’

1.1 Scope.

This document is designed to be read by programmers and artists involved in the implementation of the design of ‘Pixel park zombie runner.’
It also serves as a strict list of features to be implemented in the games design.

1.2 Type conventions.

Features which have been agreed on appear in a normal type face like this.

Features which have been suggested but have not yet been agreed on appear in an itallic type face like this.

2 Target Systems

‘Pixel park zombie runner’ is being developed for the Android operating system which runs on mobile phones and tablets.

3 Development System

‘Pixel Park Zombie Runner’ will be developed using the Unity engine.

4 Specification

4.1 Concept

The aim of ‘pixel park zombie runner’ is to produce a simple, fun, addictive game which uses pixel art graphics, retro music and SFX.

4.2 Story

The game is set in the present day.
A gentle stroll through the park goes wrong as night descends the tranquillity of the park is replaced with the stuff of nightmares as the park turns into a grave yard whose inhabitants have returned from the dead.

4.3 Game Structure

There will be several different areas in ‘pixel park zombie runner’.
These will be represented graphically by different back grounds.

4.4 Players

‘Pixel park zombie runner’ will be a single player only game.

4.5 Action

Players must control the direction of the player character (left and right) in order to avoid obstacles and enemies and to collect power ups.
Players can also purchase weapons and ammunition using the in game currency system.

4.6 Objectives

The objective of the game is to achieve the highest score possible by running for as long as possible and shooting enemy characters.

4.7 Graphics

‘Pixel park zombie runner’ will be viewed from a top down perspective and will have a pixel art style.
Player and enemy characters, coins and pickups will be represented using 2d animated sprites.
Obstacles such as grave stones will rise up out of the ground on spawning and will be represented by unanimated 2d sprites.

4.8 On screen display

The game controls and HUD will be displayed on screen.
Controls to change direction will be in the bottom right hand corner.
Weapon controls will be positioned in the bottom left corner of the screen along with the currently active power up (if any.)
There will be an option to swap the positions of the controls depending on whether the player is left or right handed.
High score, current score and the current amount of coins the player has will be displayed at the top of the screen.

4.9 Data Storage

Data including the amount of coins the player has and the high score will be stored on the target device.
The amount of coins the player has will be written to an encrypted file.
High score, weapons, ammunition and power ups will be stored using unitys playerprefs() system.

5 Action

5.1 World

The world will be made up of looping background tiles which scroll from the bottom of the screen to the top to give the impression that the player is running towards the bottom of the screen.
Once a background tile goes out of view of the camera it is removed from the game screen and added again to the list of tiles that make up the back ground.
This continues giving a looping effect.
As the player runs further, the tiles will be swapped for a different set to represent a different area of the park.


5.2 Enemies

Enemy characters will spawn behind the player at the top of the screen and will move towards the bottom of the screen moving faster than the player.
If an enemy character collides with the player, the player dies.

Enemies have certain properties such as health and they will come in different types.
Ghouls and zombies are low level enemies with a small amount of health which do not cause damage to other enemy characters.

Bulls have high amounts of health and will destroy low level enemy characters if they collide.
They will also destroy grave stones.

When enemies are shot by the player, the players score will increase.

5.3 Obstacles

During the course of the game, obstacles such as grave stones will spawn at the bottom of the screen and move towards the top of the screen at the same speed as the background scrolls.
If the player character collides with any of the obstacles the player dies.
Obstacles can be destroyed by certain weapons and certain enemies such as the bull.
When an obstacle is destroyed it will drop a ‘pick up’ item that the player can collect.
Most pickups are coins. There is a small chance that the pickup will be ammunition for the players current weapon or a power up.

5.4 Weapons

Weapons are available to be purchased from the games shop using in game currency collected in the game or earned by performing actions such as watching an advertisement video or the player inviting friends to play through facebook.
The player will also be able to earn coins by liking the big fire games facebook page (
Weapons have different properties such as: The amount of ammo which can be loaded into the weapon. The range of the weapon The amount of damage caused by the weapon when it hits an enemy character or obstacle. This will be calculated using the weapons base damage stat and the distance of the enemy/obstacle away from the player when the weapon is fired.
There are two main types of weapons:

  • Cop gun – default weapon, very short range and very small amounts of damage dealt when an object or enemy. The cop gun never runs out of ammunition. The cop gun can only damage one enemy or obstacle at a time. Desert Eagle – holds fifteen bullets until it needs to be reloaded. Has medium range and medium damage statistics. The desert eagle can only damage one enemy or obstacle at a time. The desert eagle has a medium reload time.


  • Colt Python – The colt python has short range and high damage. It can hold six bullets before it needs to be reloaded and has a lengthy reload time. The colt python can only damage one enemy at a time and can destroy obstacles.


  • Sawn off pump action – The sawn off has high damage and short range. It can hold two round until it needs to be reloaded. It has a fast reload time. It is possible for the sawn off pump action to damage more than one enemy or obstacle at a time and can destroy obstacles. Damage may be divided between the number of enemies/obstacles hit.
  • Spas12 – The spas 12 has high damage and medium range. It can hold eight rounds until it needs to be reloaded. The spas12 has a medium reload time and can destroy obstacles.

*weapons and their stats may change as the game is developed and play tested further.

5.5 Power ups

Power ups are collected throughout the game. When a player collects a power up it is automatically activated. Players can upgrade power ups to make them active for longer or have stronger effects in the shop at the beginning of the game using the in game currency.
Upgrades are permanent.
The following is a list and description of all available power ups.


  • Slow time – This power up slows down time for a set duration. The duration increases as the player upgrades the power up.
  • Shield - The shield protects the player from damage caused by colliding with obstacles or enemy characters for a duration. The duration increases as the player upgrades the power up.
  • Coin vacuum – Instead of obstacles being spawned, coins are spawned in their place. The coin vacuum draws all coins on the screen towards the player for a duration of time. The duration increases as the player upgrades the power up.

5.6 Currency

Coins can be used to buy weapons, ammunition and power ups from the in game shop at the beginning of every game.
Coins can be collected during the game from the play area. A small amount is spawned randomly. Each obstacle which gets destroyed drops a coin in its place.
Coins can also be ‘earned’ by the player by watching a video advert (around 30 secs) or by inviting their players to play the game using facebook.

5.7 Controls

The player has controls to fire his or her weapon and to control the direction of the player character.
The weapon button fires the gun at the closest enemy or obstacle depending on the weapon type.
The direction button flips the players movement on the horizontal axis from left to right or right to left depending on the players current direction of travel.

If the player hits the side of the screen he or she will either die or their direction of movement will be reversed.

6 Front end

6.1 Introduction scene

The introduction scene will feature a coin-op style attract mode.

6.2 Menu
The games menu will double as the title screen and has the following options:

Run – this button starts the game.

Options – this button opens up the options screen where the user can change several options such as the control positions and turn the music on and off.

Shop – this button opens up the in game shop.

Facebook button – This button lets the players earn in game currency by inviting their facebook friends to play ‘pixel park zombie runner.’

Earn coins – this button allows the player to earn coins by watching a 30 second video advert.

6.3 Shop

The in game shop is where the player can spend coins to buy weapons, costumes and upgrade power ups.

7 Team

Paul Tricklebank – Programmer, Game design, Art.
Some art will be created by freelance artists.






The entire game design document can be downloaded here

Feedback is always welcome :)


You can find me and Big fire games on twitter and Facebook

Paul Tricklebank

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