Here is the full list of all 13 Comet 64 achievements.
Get every star in the game
Get the secret star
Enter the correct password to access voodoo.txt
Solve all puzzles in Disk B
Solve all puzzles in Disk A
Solve all puzzles in Disk 4
Solve all puzzles in Disk 3
Solve all puzzles in Disk 2
Solve all puzzles in Disk 1
Solve 'Must Come Down' in exactly 3 lines and 303 cycles
Solve your first puzzle.
Play the secret ending
Play the real ending