With each wave of enemies will increase power and eventually you lose. This ensures the player’s involvement for many hours to achieve the goal. To withstand more waves you need to upgrade.
There are two resources for upgrading:
1. Gold. For gold, you can update your damage, defense or economy. This will help live you to much longer
2. Diamonds. They are hard earned, but in the store with their help you can buy updates for yourself, which will be active from the start of the next game.
Example: now you have 2 damage and every time you lose, then again you will have 2 points of damage. If you buy 1 point of damage for diamonds, then after each loss you will have 3 dmg (not 2). This works until you get bored or until there are diamonds.
This game is optimized as much as possible. Pixel graphics will work without problems even on weak devices.
It is also possible to compile the game for Android and IOS systems. This will not cause you difficulties.
There is an opportunity to embed advertising. Banner or interstitial ad
And most importantly: you can adjust the cost of updates as you want. The documentation specifies how to do this