Sum Slide

Sum Slide is mental arithmetic on a snowy mountain. A sum appears on a wooden signpost in big digits, such as four plus three, twelve take away five or seven times eight, and three penguins wait at the top of three icy slides, each holding up an answer card. Tap the penguin with the right answer and it throws its card in the air and whooshes down the slide to the finish line, where a growing crowd of penguins cheers it in. Tap a wrong one and it just wobbles and stays put. There are no lives, no timer and nothing to lose, and after a second miss the right penguin glows so nobody gets stuck.

Three big buttons on the title screen pick the level. 4+ is adding and taking away within ten, with dots under every number to count and a number line that hops to the answer after a second miss. 6+ goes up to twenty, then to a hundred in tens, with doubles and number bonds to ten and twenty. 8+ brings the times tables from two to ten, division as sharing fish between plates, two-step sums and a make-the-target puzzle: choose two of four cards that add or multiply to the number on the sign. Some sums have a gap instead, like 3 + ? = 7, and you drag a card from a penguin into it. The first time a new kind of sum turns up, a cartoon hand shows how it works, so nothing has to be read.

A round is ten sums, and finishing one earns stars, a rising learned meter for that level and a new sticker for the sticker book: sixteen mountain animals, from a snow leopard and a red panda to a yak, an ibex and a pika. The daily round gives everyone the same sums for the day and hands out the daily sticker. At 8+ there is also a quick mode for a brain warm-up, where a snowball rolls slowly along the ridge and you answer as many as you like before it reaches the snowman. It never fails you, it just counts, and your best count is kept as a high score. The music is a soft music box, the pace is relaxed, and it all works with a finger, a mouse or the number keys, with progress kept in your browser.