Gem Roller

Gem Roller is a 3D marble game set on floating sky islands. Each level is a hand-built course of grassy tiles, ramps, half-pipes, narrow planks and moving platforms with gems scattered along the way and a pulsing goal ring at the end. Roll through the ring to finish and you earn a star; collect every gem for a second and beat the par time for a third. Levels take well under a minute, so a quick retry for the missing star is always tempting. Roll off the edge and the marble pops back at the last checkpoint after a short fade, and the clock keeps running.

Forty levels are spread over four worlds, each with its own sky, palette and scenery. Meadow Islands starts gently with hills, bumpers and springy bounce pads. Crystal Caves adds slippery ice, half-pipes and moving platforms under glowing crystals. Lava Forge brings fans that push you sideways and narrow bridges over a sea of lava, and Cloud Temple lets you jump across the gaps between marble pillars. Every level keeps your best time and stars, and your best scores add up to one high score. Choose your marble from ruby, sapphire, emerald, amber, a soccer ball or a disco ball, and try the Playground, a free level with no clock.

Roll with the arrow keys or WASD: the controls follow the camera, which swings round the corners and lifts over edges so you can see the drops coming. Space jumps on levels that allow it and R restarts. On a phone or tablet a joystick appears wherever your left thumb lands, with a jump button on the right, and tilt steering can be switched on from the pause menu on phones that allow it. Your progress is saved in your browser. P pauses, M mutes.