Bolt Buddy

Bolt Buddy is a screw puzzle with real physics for your phone, tablet or computer. Bolty, a small robot mechanic, runs a workshop full of broken toys and gadgets. Every level is a machine of colourful plates held to a board by screws, and a toy, a kitten or a treasure is stuck behind them. Move the screws in the right order, let the plates swing and drop off the board, and rescue what is hidden inside before the clock runs out.

How to play

• Lift a screw: tap it. It rises out of its hole. Tap it again to put it back, or tap another screw to pick that one instead.
• Put it somewhere else: with a screw lifted, tap an empty hole. The holes it can go into glow. On a computer you can also use the arrow keys to choose and Enter to tap.
• Covered holes: a hole under the solid part of a plate is blocked. If that plate has its own hole lined up right over the board hole, the screw can go in, and it then holds that plate again.
• Stacked plates: one screw can go through several plates at once. Pull it and all of them come loose there.
• Swing and drop: a plate held by two or more screws stays still. With one screw left it swings around it like a hinge. With none it falls off the board.
• Plates rest on screws: plates pass through each other, but a swinging or falling plate can land on another screw and get stuck there until you move that screw.

Drop every plate to win. You only get one spare hole, in the tray at the top, so the real puzzle is where to park each screw. More holes are hidden under the plates and open up as the plates above them drop or swing away, so the order you work in matters.

Five workshops, fifty levels

The game has five worlds of ten levels each: the Toy Room, the Kitchen Gadgets corner, the Snowy Garage, the Clock Tower and the Space Lab. Every world adds something new. Locked holes can be opened for coins. Rusty screws need a tap to loosen before they lift. Chained screws lock their partner for one move. Frozen screws thaw only after enough plates have dropped. Magnet screws have to be moved in number order. The golden key screw opens every locked hole. Big plates have three or four holes, a bomb plate must drop before its counter reaches zero, and in the Space Lab the plates float down in low gravity. Every tenth level is a boss machine, and the last one is the Mega Spaceship.

Every level has been proven winnable: a computer player found a way through each one, and that exact list of moves was replayed with the real physics to check it. Levels are built from a fixed seed, so level 23 is the same puzzle for everyone.

Boosters, stars and coins

Hint shows a good next move, Undo takes back your last move (plates that fell come back too), Unscrew pulls any screw out of the board, and the Hammer smashes a plate. When time runs out you can buy an extra minute. You start with a few free boosters, and after that they cost coins, which you earn by finishing levels. Finish quickly for three stars; using a booster costs one star.

Tips

• Before you pull a screw, look at what will swing. A long plate hanging from its last screw can cover the holes below it.
• Pull the second screw of a plate soon after the first, so it drops instead of hanging in the way.
• Think before you fill the spare hole. If every hole is full or covered, no screw can move.
• A plate resting on a screw is not stuck forever: move that screw to a spare hole and the plate drops.
• On bomb levels, work on the bomb plate first. Every move, including loosening a rusty screw, counts down.

Play it anywhere

Bolt Buddy runs in your browser with nothing to download, on any phone, tablet or computer. The physics uses the open-source Matter.js engine, and the sounds are made by the game as you play. You can switch sound and vibration off in the menu. Your progress, stars and coins are saved on your own device. The game is free, has no pop-ups inside it, and is friendly for players of every age.