Here is the full list of all 18 Escape Zolstar achievements.
Defeat the first boss.
Defeat the second boss.
Defeat the third boss.
Defeat the fourth boss.
Defeat the fifth boss.
Defeat the sixth boss.
Collect a health powerup.
Collect all health powerups.
Collect a rapid fire powerup.
Collect all rapid fire powerups.
Complete the game with no health powerups.
Complete the game with no rapid fire powerups.
Complete the game with no optional powerups.
Complete the game with 10 or less deaths.
Complete the game with 0 deaths.
Complete the game in 60 minutes or less.
Complete the game in 40 minutes or less.
Complete the game in 20 minutes or less.