Tap a bolt, lift the nut off the top, drop it on a nut of the same colour. That is the whole game — and by level thirty you will be sitting there working out which of four moves is the one that doesn't end in a dead end.

Screw Sort is a nuts and bolts puzzle with a garage behind it. Sort the board, earn wrenches, and spend them turning a wreck into a car worth looking at.

■ 200 LEVELS THAT KEEP MOVING
The difficulty doesn't climb in a straight line. Every tenth level is a breather, every twenty-fifth is a proper wall, and new rules keep arriving the whole way through instead of running out in the first hour.

■ FOUR THINGS THAT GET IN YOUR WAY
Short bolts hold fewer nuts — somewhere to put a nut down, never somewhere to finish a stack. Padlocked nuts open after a few moves made anywhere on the board, and the lock shows how many — so you plan around them. Welded pairs move as one piece and need two free slots at once. Painted bolts are home: anything can pass through, but their colour can only be finished there.

■ HIDDEN NUTS
Some nuts keep their colour secret until the one above them is lifted. You can plan for it, or go on a hunch and keep an undo in reserve.

■ REBUILD THE CAR
Every garage is a wreck in stages: paint, wheels, engine, interior, doors. Parts fly in and bolt themselves on as you pay for them. Finish one car and the next garage opens.

■ WHEN A BOARD GETS TIGHT
Two boosts: take the last move back, or grow yourself one extra bolt. And if a board really has no moves left, the game says so — you are never quietly stuck wondering.

■ BONUS LEVELS AND THE WHEEL
Harder boards slipped in between the regular ones, for a bigger payout. Plus a daily spin of the wheel for coins, wrenches and boosts.

HOW IT PLAYS
- 200 sorting levels, every one checked to be solvable before it shipped
- No timers and no lives — think for as long as you like
- A short tutorial for the first moves and both boosts
- A garage to restore, one car stage at a time
- Leaderboard, profile and a character to pick
- The puzzles work offline

A quiet logic puzzle for three minutes in a queue, or an hour on the sofa.