Marble Run

Marble Run is a wooden marble track you build on a sunny playroom wall. A pegboard fills the wall and a tray holds the pieces: straight ramps that run left or right, curves, a U-turn, a funnel, a glass loop, a rubber bumper, a trampoline, a spiral, a brass bell, a lift that carries marbles back up, a splitter that sends them left and right in turn, and a glass cup to catch them. Drag a piece onto the grid and a ghost shows where it will snap, tap it to turn it, then press Test: the marbles drop from the start tube and roll, bounce, ring and loop under real physics, and Back puts your build exactly as it was.

Forty challenges give your brain something to chew on. Each wall has a fixed start and cup, a handful of pieces in the tray and a goal: get three marbles into the cup, ring the bell, send a marble round the loop, share four marbles between two cups or keep one rolling for ten seconds. Every challenge has three stars to earn: meet the goal, stay within the piece budget, and pick up the three gold stars along the way. Each one is quick, a minute or two, and your stars are saved in your browser.

Free build is a big empty wall with every piece unlimited and up to twenty marbles at once, each one a different colour. Build a contraption, switch on calm mode and the marbles go round in an endless loop through the lift while the bell rings and the spiral turns, so you can sit back and relax. Save up to twenty runs, take a photo of your favourite and pick up where you left off next time. Undo and redo go fifty steps back, and it plays with a mouse, a keyboard or a finger.