What is Lethe
Lethe is a grid puzzle where the laws of physics are things you carry in your head. You steer a small figure through fifty rooms, looking for the exit. A wall in the way is not broken: you forget that solid matter resists, and walk through the stone. A pit ahead is not jumped: you forget gravity and drift over it. Five beliefs sit beside the board, gravity, fire burns, solidity, weight and permanence, and clicking one erases it at once. Crates and pressure plates obey your new, smaller set of rules too.
The difficulty comes from an asymmetry. Forgetting costs one move and happens the instant you ask. Remembering is not your choice: the world has to prove the rule in front of you. Gravity returns when you watch a crate fall, solidity when you see one land, fire when wood burns. So a level is rarely about which path to take. It is about order, and the same three actions in a different sequence build completely different worlds.
How to play
- Move with the arrow keys or WASD and reach the exit tile. Press Z to undo a step, R to restart the level.
- Click a belief in the sidebar, or press its number from 1 to 5, to forget it. Forgetting counts as a move.
- Beliefs return only through observation: a falling crate restores gravity, a landing crate restores solidity, burning wood restores fire, your own landing restores weight, anything destroyed restores permanence.
- Stand on a numbered plate, or push a crate onto it, to open the barrier with the same number. Finish at or under par for gold, and your run score adds up every level you clear.
Strategies that work
- Plan the order of forgetting before your first step. Dropping solidity while you still believe in gravity makes the floor stop holding you, and you fall out of the map. To pass through stone, forget gravity first, solidity second.
- Never let a belief return while you are in a bad place. Believing in solidity again inside a wall or a crate kills you instantly, and remembering fire inside a flame does the same. Step onto open ground first.
- Weight and gravity drive the machinery. Crates fall only while you believe in weight, and a plate feels you only while you believe in gravity. A weightless player can cross a plate without arming it, then return to press it later.
- Permanence is the switch for your plates. Keep it and a weighted plate stays locked, so a barrier stays open behind you. Forget it and the plate releases as soon as the weight leaves, the only way to close a barrier again.
- Restarting is free, undoing is not. Each undo costs 15 points and each death 50, but pressing R rebuilds the level and resets your moves, undos and deaths to zero. After a death, restart rather than undoing back through it.
A little history
Lethe is an original game, not a version of anything older. The name comes from Greek mythology, where the Lethe is a river of the underworld whose water erases memory; the word itself means forgetting. The puzzle belongs to the tradition of block-pushing grid games that runs from Sokoban to the modern wave of puzzles built on one unusual rule, and to the narrower strand where the rules of the simulation are the pieces you move. What it adds is the price of a rule's return: removing one is free, restoring it is a physical event that must happen in the world.
Frequently asked questions
How many levels are there, and is my progress saved?
Fifty. The first six introduce one belief each and the rest combine them. Your best move count per level and the local leaderboard are stored in your browser, so unlocked levels are waiting when you return. Clearing the same level twice in one run does not score twice.
A belief came back on its own. Is that a bug?
No, it is the central rule. Beliefs return whenever the world demonstrates them in front of you, and you cannot block that in advance. A crate falling anywhere restores gravity, even when you would rather keep it forgotten. Controlling where crates fall is much of the game.
Can a level become impossible without killing me?
Yes. A crate lost in a pit or burned in fire is gone for good, and some barriers never reopen once closed. The game does not announce a dead position, so if you destroyed something you needed, undo with Z or restart with R at no score cost.
