Here is the full list of all 21 Tachyon Project achievements.
Finish the fourth level
Finish the fifth level
Destroy 10 enemies with a single explosion
Finish the third level
Destroy 2500 enemies
Destroy 100 bulls
Destroy 100 Shield Bearers
Finish the first level
Finish the second level
Destroy 500 enemies
Finish the sixth level
Finish the seventh level
Finish the eighth level
Finish the ninth level
Finish the tenth level
Kill 50 enemies in less than 1 second
Destroy 10000 enemies
Leave a Decoy and a Turret right after
Finish a wave with less than 1 second left
Spend 15 seconds hidden in one go
Spend a total of 10 minutes hidden