Impossible to Pass Level 42

Forty-one warm puzzles, then one built to fight back

impossible to pass level 42! — its own maker shortens it to itpl 42 — is a free iPhone logic puzzle with an unusual structure: forty-one fair, machine-generated levels, followed by a forty-second board built by hand specifically to be neither fair nor generated.

The setup reads simply. Capybaras need seats on an n×n grid, and the grid is also divided into n pools. Four rules govern every board:

• One capybara per row, and one per column
• One capybara per pool
• Every capybara must sit next to a hot spring
• No capybara may occupy a rock

Each rule is easy alone. Stacked together across a full board, they stop being easy — which is the entire premise of the game.

The one-solution guarantee

Every board, all forty-two of them, is verified to have exactly one valid solution. That's not a marketing line, it's a constraint the generator enforces directly, which means there's no ambiguity to blame when a level feels impossible. If you're stuck, the fix is a placement you haven't found yet, not a broken puzzle.

The first forty-one boards come from that generator: tuned, tested, reasonable. Board 42 skips the generator entirely. It's hand-built by the developer, using knowledge of exactly which shortcuts a solver reaches for — and closing each one off in turn.

Why it's worth a look

Most puzzle apps either stay easy forever or ramp up gradually. Here, the difficulty curve is flat for forty-one levels and then vertical for one. It's a small, deliberate design choice that turns the last level into something closer to a dare than a puzzle — and it's the whole reason the game's own copy says the solution is "left as an exercise for the reader."

Try it: itpl42.com — free on the App Store, built by Little Tough Team.