Lost MonstersAbout Lost Monsters
Lost Monsters is a free sliding puzzle game for the browser. Five monsters are lost in a cave, and you bring the green one home in as few moves as possible. It runs on phones, tablets and computers, without a download, an account or a sign-up.
The monsters
There are five of them, and they all follow the same rules: they slide in a straight line until a wall, a pit or another monster stops them. They only differ in looks and character.
| Monster | Colour | Part in the game |
|---|---|---|
| Roland | green | The one you bring home. He is the lively one, always ready to go. |
| Harry | yellow | A helper and stopper |
| Griffin | red | A helper and stopper |
| Goof | blue | A helper and stopper |
| Louiii | pink | A helper and stopper |
The four helpers are the real puzzle. Roland can rarely stop on the exit by himself, so you move the others into place first, and he slides home against them. The puzzle guides show how that works on real boards.
Where the game comes from
Lost Monsters started as a mobile game, built with the Unity engine. It had the cave, the five monsters with their animations and sounds, and online features such as accounts and challenges between friends.
Its puzzles were made in spring 2019. A program placed the monsters at random on five hand-drawn cave maps, and a solver tried every possible sequence of moves to find the shortest way to bring the target monster home. Boards that were too trivial were dropped. What was left are the 3,927 challenges you can play today, each with a proven best solution.
In October 2026 the game was rebuilt for the web as lost-monsters.com. The art, the animations, the music and every challenge come from the original; the code is new and written for the browser. The online parts were left out: there is no account, and your progress stays in your own browser.
How the difficulty is decided
The number of moves alone is a poor measure of difficulty. A four-move puzzle can be hard if the first move is one nobody would think of. So every challenge is played many times by four simulated players of rising skill: a novice who only moves the green monster, a casual player who plans three moves ahead and sees one helper move, an advanced player and a pro who plans five moves ahead with two helpers.
A challenge is Easy if the casual player earns three stars on it in at least half of its games, and Medium if the advanced player does in at least a quarter. Everything else is Difficult, including about a thousand boards that even the simulated pro rarely solves well. That is why there are 505 Easy, 820 Medium and 2,602 Difficult challenges. Within a level, the game picks boards that fit how well you have been playing.
Because every challenge has a known best solution, the stars are fair: five stars, shown as the crown, means you found a solution as short as the best one there is. After every win you can watch that best solution move by move.
Who makes it
Lost Monsters is made by Philipp Kölmel in Hamburg, Germany, as an independent project. The game is free. It may show one short ad between two games after several minutes of play; that is what pays for it. What changes is listed on the News page.
Questions, ideas or a board you think is broken? Write to info@lost-monsters.com. Legal details are in the imprint, and what the game stores and measures is in the privacy policy.