Here is the full list of all 22 Cube Defender achievements.
Started hard mode for the first time
Bashed over 5000 cube into oblivion, the cubes fear your might
You must really hate those cubes, you destroyed 500 of them!
Started Cube Defender in easy mode
Started the game on normal difficulty for the first time.
Annihilated over 2000 cubes!
Unlocked and built all of the turrets in a single game
Unlocked, built and upgraded fully at least one of each turret in the game
Completed Cube Defender on easy mode at least once
Completed the game on normal mode at least once. Give hard mode a go!
Completed Cube Defender on hard mode at least once.
Sold over 100 turrets in the game
Sold over 50 turrets in the game.
Let at least 50 cubes escape the game zone. Whoopsie
Failed to destroy all of the cubes. Lost your first game.
Earned over 20,000 units of currency
Earned over 100,000 units of currency while playing the game
Let at least 100 cubes escape while playing. You need to watch those cubes!
Destroyed at least 20 boss cubes
Destroyed at least 50 cube enemies with stealth
Spent over 20,000 on turrets, updates and other things.
Earned over 100,000 score points across one or more games