Sky Stack: a multiplication blocks game

How to play

You run the crane on a building site. Each tower is built from one table, say the 7s, and only its multiples (7, 14, 21… up to 84) make good floors. The crane swings in one numbered block at a time. Is it in the 7s?

1. Pick one or more tables, or Mixed 2–12, and press Start. With several tables, each tower uses a different one.
2. If the block is a multiple, press Stack (↓ or Space, or swipe down). It drops onto the tower and becomes a floor labelled with its fact: 6 × 7 = 42.
3. If it isn't, press Toss (→, or swipe right) and the crane flings it away.
4. Stack a block that isn't in the table and it cracks, falls off and the tower wobbles. Three wobbles knock the top floor off. Toss a block that belonged and the game tells you which fact it was.
5. Each tower has 16 blocks (10 of them belong) and needs 8 floors. Build three: a day tower (×1 to ×10), then a sunset tower and a night tower (both ×1 to ×12) with sneakier impostors. There are 24 floors in all.

There's no timer: take as long as you need over each block. Reduced motion: blocks drop straight into place, the crane and tower don't sway, clouds stay still and nothing flies off the screen.

What it teaches

Sky Stack turns a times table into a yes-or-no question: is this number one of the 7s? That's a different skill from answering “7 × 6 = ?”. Players have to know the whole table well enough to spot the impostors, which is what they need later for factors, simplifying fractions and division.

• Day tower, far impostors: numbers like 17 or 25 among the 7s are a few away from any multiple, so players can rely on skip counting.
• Sunset tower, near misses: 43 right next to 42, or 54 just under 56. Counting on from a known fact sorts them out.
• Night tower, look-alikes: 48 (which is 6 × 8, not a 7s fact) or 24, the digits of 42 swapped. These traps need real recall.
• Every floor is a fact: each stacked block shows its fact, so the finished tower holds eight facts from the table, ready to read top to bottom.
• Reasons, not just red crosses: a wrong block shows the two multiples either side (“45 isn't in the 7s: 6 × 7 = 42 and 7 × 7 = 49”), which builds number sense.