Hey!

There are 6 achievements:

1: Finished - Finish the game (beat all 16 levels).
2: Again - Start a new Game (start a new game a second time).
3: Pacifist - Complete the game without killing more enemies then necessary (you can kill only the very first 'dark cloud' that you encounter; you must avoid all the others).

The other three achievements are for finishing the game under certain times:

4: Speed runner - Complete the game in less than 30 minutes.
5: Speedier runner - Complete the game in less than 20 minutes.
6: Lightspeed runner - Complete the game in less than 7:41 minutes.

Under 30 and 20 minutes can be done without much preparation- as long as you don’t waste too much time and are somewhat familiar with the puzzle mechanics, you should be able to unlock these.

As for 7:41- you have very little time to spare, maybe a minute or so. The timer pauses while the game is paused, so you can look up solutions without rushing.

0:00 = Intro/Level 1
0:12 = Level 2
0:25 = Level 3
0:36 = Level 4
0:54 = Level 5

1:11 = Level 6
1:26 = Level 7
1:57 = Level 8
2:16 = Level 9
2:44 = Level 10

3:15 = Level 11
4:00 = Level 12
4:30 = Level 13
5:02 = Level 14
5:30 = Level 15

6:23 = Level 16/Ending

If you have any questions, suggestions, criticisms, found any mistakes and so on, please let me know!

Thanks to the developers for making a good game and thank you for checking out my guide!