The titular Hap has to clear each screen of bombs as soon as possible. There is a global time limit for all screens combined. If the 30th level is reached before time runs out, you can catch the evil guy planting all those bombs. If not, game over.
As with Jumpman, the point of the game is that every level (save the first) has its own gimmick, ranging from moving platforms to weird enemies, and from a rotating laser to darkness.
- Excuse Plot: There's little else to the game than clearing bombs.
- Green Hill Zone: As with Jumpman, in the first level nothing much happens.
- Moon Logic Puzzle: The game is utterly impossible until you figure out that dying right as you complete the level adds two minutes to your clock.
- Power-Up Letdown: In the levels where you can shoot a gun (or a mega laser) you can no longer jump.
- Time Limit: You get infinite lives, but finite time.
- A Winner Is You: The ending just states "mission complete!"