I am currently working on a tower defense game, and I am having trouble figuring out how to implement the cost of turrets, upgrades, and the gain from completing a level, killing an enemy. Below is a summary of the requirements:

  • There are multiple types of turrets, each turret has different properties, such as reload speed, range. Each upgrade has multiple levels.
  • Each turret can have multiple types of ammo, each ammo type can have different upgrades, such as blast range, damage, addons. Each upgrade has multiple levels
  • The sources of income are
    • killing enemies, each enemy has a different value
    • completing a level

My problem is with balancing everything so the game is at least playable, or in the right direction to get balanced by testing it. I know there is no magic formula for this but I believe people with experience will know where to start, and what process to follow. So my questions are:

1- is there a method to calculate the cost of turrets, upgrades? what factors should I take into consideration? 2- Should I use two different currencies for upgrades and turret purchases? 3- How to calculate the upgrade cost as the upgrade level increases? i.e. when the user purchases more of the same upgrade.

  • 6
    \$\begingroup\$ Excel is your friend. Calculate the cash earned by level, and think of how many levels before a player "should" be able to buy something -- there's the cost right there. \$\endgroup\$
    – ashes999
    Nov 21, 2013 at 4:38
  • \$\begingroup\$ If this was my question, I'd accept the comment from @ashes999 as the answer. There really isn't much else to it but the good old brute-force calculating it all, which is so much easier with excel. \$\endgroup\$
    – Lasse
    Nov 21, 2013 at 6:37
  • \$\begingroup\$ There likely is a magic formula, but you have to discover it yourself because it is derived from your game mechanics. \$\endgroup\$
    – Philipp
    Nov 22, 2013 at 12:49
  • \$\begingroup\$ You need to read the game balance concepts course \$\endgroup\$
    – o0'.
    Apr 14, 2014 at 13:31

2 Answers 2


Excel is your friend. Calculate the cash earned by level, and think of how many levels before a player "should" be able to buy something -- there's the cost right there.

Here's a simple example. Imagine, for simplicity's sake, two turrets with two ammo types each.

  • Turret 1: slow/ranged. Ammo is artillery shells and grenades.
  • Turret 2: fast/close. Ammo is bullets and lasers.

You want T2/Bullets in level 2, T1/shells in level 3, T2/lasers in level 6, and T2/grenades in level 10.

Further assume you get N * 100 gold for completing level N (eg. 100, 200. ...). In this case, it's easy to calculate the following costs:

  • T2/Bullets: 300 (100 + 200)
  • T1/Shells: 600 (100 + 200 + 300)
  • T2/Lasers: 2100 (100 + 200 + ... + 600)
  • T2/Grenades: 5500

Tweak your formulas and parameters accordingly until it seems right. Then playtest it and see if it feels right.


Extending the comment made by @ashes999: Make a big Excel spreadsheet, then calculate every metric you can get. This includes:

  • How much cash gain per level (starting gold, gold per monster)
  • How many Enemies can each update / ammo combination take out in a single wave
  • Based on above Information: Which tower combination is viable for this level
  • How much would each of this combination cost

With this you could do a lot of stuff:

  • Calculate the maximun and minimum amount of gold needed to win this level.
  • Decide how much gold you want to provide (maybe based on difficulty setting)
  • Adjust starting gold and gold per enemy

Hope this gets you started!


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