Tower Defence Game Design Document


In my game, you play as a blood mage who must defend their summoning altar from an army of pesky do-gooders and knights trying to stop your plan to take over the world. To protect your interests, naturally, you summon an army of demons, monsters and more to obliterate your attackers. As blood is spilt, your power grows, giving you access to demons as strong as Satan himself.


This tower defence game allows the player to become the villain and be the one corrupting the world with monsters. The game will be split into rounds of enemy attacks. These enemies will follow a set path across the level map, that the player will be able to clearly see and follow. Before each wave, the player will have the opportunity to summon units to defend the pathway.

With each enemy defeated, the player gains a small amount of blood – this game’s currency – that they can use to summon more monsters in the future. The player can also spend blood to upgrade monsters that they have already summoned, to make them more powerful than before.

To complete the game without losing, the player must successfully defend against all the waves of enemies without letting too many through as the player will have a limited number of lives.

Game Mechanics


Tower Defence

The player must defend their precious blood altar from an onslaught of “good guys” trying to stop their grab at world domination. This brings in the tower defence theme: the player can summon units to different locations along the enemy route to destroy any enemies that come within range.


Blood mages are notorious for summoning creatures of twisted origins, created through sacrifices on their altars. I wanted to give the player the chance to experience the power of the dark arts and to revel in the magic at their disposal.


What actions can the player take in the game?

Summon Monsters

Pick a monster that you want to summon and place it if you can afford its blood cost.

Upgrading an individual monster to make it deadlier.

Dismiss Units

If a monster is no longer fulfilling its purpose, the player can banish them back to the void where they came from. This creates space that the player can use to summon other horrors.

When the player dismisses a monster, they will get a partial refund for the original summoning cost.

Pause the Game

The player can, at any time, choose to pause the game to adjust settings or exit the game.

The Story

Main Story

You were raised as a blood mage by the Cult of Cthulhu, destined to bring about the world’s end. Finally, after years of planning and preparation, your time has come. Unfortunately, the leaders of the world are none too happy about your plans to destroy it and have sent their finest warriors to defeat you, too bad you have all of hell on your side.


The game will end when the player has taken too much damage to continue to summon monsters, or when there are no more waves of enemies to defeat. If the player is defeated, the world will return to normal, and any monsters that they had summoned will escape to the void. However, if the player is victorious, the world will be overrun by the creatures that you have summoned.


Whenever the player’s monsters kill an enemy, the player gains a new supply of fresh blood to use to summon more monsters. As you defeat more enemies, your blood stores fill, allowing you to summon stronger and more powerful minions than before. You can also use your supply of blood to upgrade your existing monsters by feeding it to them.

User Interface

At any time, the player should be able to see how much blood they have that they can spend to summon more monsters, especially if the player is able to summon during an attack wave. Furthermore, when the player is considering which monster to summon, they need to be able to see a variety of information about that monster, such as cost, damage per second, damage type, and range. If the player is able to summon during an attack, then the menu for monster summons must not cover the screen at this time, or the game must pause while the player considers their options.


Start of Round

At the beginning of each round, the player will be able to use their supply of blood to summon some monsters before the enemies begin to attack. Once the player is happy with their troop placement, they can opt to start the round. This will cause the enemies to begin to follow the path.

Between Waves

After a round has completed, the player will have the opportunity to summon more creatures, dismiss any creatures they already had on the map, and upgrade their monsters. This also gives the player a chance to take a pause and think up a strategy for how they want their units placed for the upcoming attacks.

Enemy Behaviour

The monsters that you summon will have to automatically attack enemy units within range when their attacks are not on cooldown, as this is the main mechanic of a tower defence game. Furthermore, the enemies must follow a set path across the map, through the field of monsters.

Sound Effects

I want to add atmosphere to the game through the use of eerie music and sound effects. I would like to be able to work with a sound design student at another university if possible, so I can work with people from other disciplines, and practise co-ordination within a small team who are creating different parts of the same project.


Since the game revolves around summoning monsters and mythical beasts to do your bidding, I want to create a dark atmosphere to make the game feel like you are overrunning the world with evil.

I would like to be able to create most of the visual assets for the game myself where possible. I will design creatures and their attacks on paper, before transferring these ideas to a digital medium. I will use pixel art as it gives me the freedom to create simpler animations, that will require less frames.

Technical considerations


How can the player place units?

In some tower defence games, the player is only able to place units within the bounds of a grid. In others, the player can place units freely, so long as they aren’t on the enemy path, or overlapping with one another. Before I begin creating my game, I need to decide which of these two methods to use.


Future Additions

  • Time control: The player would be able to pause/play the flow of the game at any time, as well as speed up the pace of the game to make levels pass faster. This is a common feature in tower defence games.


  • World progression: As the player progresses further into the game, the time period could change. The player would start out facing knights and peasants, but as time passes, they may have to face guns, flamethrowers and more.


  • Different enemies: Inside of a wave of standard enemies, there could be a few more advanced troops, with greater armour or that move faster, to make each wave more interesting, and to encourage the player to vary their monster placement in response.


Wireframes for Mech Builders

Mech Builders is puzzle game where you unlock mech parts to build a fighting robot with which to crush your enemies! At the start of the game, you are shown the power level and stats of the mech you will be battling against, before being taken to a puzzle select screen. If you are successful in beating the puzzle you gain a new part to use for your mech. However, you can choose to try a harder version of the same puzzle to have a chance of receiving an upgraded part. If you opt to do so, and fail to complete the puzzle, then you will lose the part you chose to risk.

Once you have completed all the possible levels for the mech match, the two mechs will fight each other until one of them falls apart and loses. To progress in the game you have to build bigger and better mechs, defeating powerful foes along your way to dominance.

My initial sketches

I initially designed my wireframes on paper, so I could get my first ideas down to be iterated upon. Then, I moved into Axure to create digital wireframes of each of the five screens.

Title Screen

The first screen I created was the title screen. I kept all the key buttons the player would need in the centre of the screen. By surrounding those buttons with cogs on either side and an image of a selection of mechs in the game at the bottom, I can draw the eye into the middle of the screen, making the menu options easy to find.

Enemy Mech Stats

Once the player has opted to start a new level, they are shown the stats of the enemy that they are going to be attempting to defeat. They can view this screen any time from the pause menu, so that players do not need to memorise a lot of information as they play. On the left, there will be an image of the mech in its signature pose, ready for battle. The same image will be used later in the mech comparison screen, to give the game consistency. On the right, there will be a slowly rotating model of the mech, giving the player a 360 view of what the mech looks like. I put the challenge them button at the bottom of the screen to encourage the player to at least skim-read the enemy stats before starting the level.

Puzzle Selection

After the player has hit challenge them on the enemy mech stats screen, they will be taken to the pick a puzzle screen. The exact number of puzzles that the players will be able to choose from is currently unknown, however it could change based on how far through the game the player is. When they are facing more challenging mechs, they will have less puzzles to choose from so they have to be more careful when it comes to risking components.

Each image for a puzzle will give a vague hint as to the type of puzzle it is, as well as what component you are likely to get from completing the puzzle. I gave the player the option of viewing their mech and the enemy mech at the bottom of the screen so that they have a better understanding of which parts they still need to collect or if they have one of each part, which ones they should try another puzzle for to get a better version.

Use It or Risk It

This screen is shown to the player each time they successfully complete a puzzle. On the left, the enemy mech is shown to keep the layout consistent, as in other comparison screens the enemy is also shown to the left. Players have the option to either read a detailed description of each components with their strengths and weaknesses, or they can quickly glance at the overall component ratings given underneath the picture of each part. I made the use it and risk it buttons bold and large on the screen, to draw the player’s attention to the decision that they have to make before they can continue.

Mech Comparison

The mech comparison screen is shown to the player right before the mechs go head to head in battle. It gives a detailed description of each mech, as well as a bar chart which gives a direct comparison of specific key stats that will show which way the battle may swing. The placeholder on the left is the same posed image of the enemy mech that the player is shown on the enemy mech stats screen. The placeholder on the right serves a similar function for the player created mech, except the pose is generated based on the overall rating of the mech so that weak mechs will pose in ways that makes them look delicate whereas high-tier mechs will pose like a stereo-typical wrestler.


I found working out a basic layout idea on paper was beneficial to my overall designs as it allowed me to get my initial ideas out to be refined further. This is useful particularly if you want to iterate upon your sketches before moving onto the wireframing stage. Wireframes are useful as they allow you to see how the game will flow between screens and identify how large different elements have to be on the screen to make them usable.

From this wireframing project, I have learnt how to use Axure to create pixel accurate wireframes. I have also spent time considering how layouts can change based on platforms, as well as how much information you can fit on a single screen based on the size of that screen.