As the description says, you need to finish the game in 79 seconds! Suggested doing after playing through at least once. So start the game, New Game, and skip the intro.
For each level, enter the following and press Enter, then exit the level immediately afterwards by pressing Escape, before moving onto the next one:
Level 1: "p"
Level 2: "proton sphere" (you might want to have this one copied so you can just paste it into the game)
Level 3: "p"
Level 4: "burn"
Level 5: "ra"
Level 6: "filth"
After Level 6 you'll get the "you beat the game" screen. Press the Escape button here to go back to the main menu. The achievement should pop if you were quick enough, but you might actually have to start another New Game according to some.