Sum Pyramid
Every brick is the sum of the two bricks below it. Fill in the missing numbers, working up and down the pyramid, then meet product and difference pyramids and the clever middle-brick trick.
Play nowHow to play
Controls
TapKeyboard←→↑↓- Tap a blank brick, type its number on the pad and tap OK.
- Each brick equals the two bricks under it combined by the rule shown at the top: plus, times or the difference.
- If you know a brick and one of the two below, you can work out the other.
- Five wrong bricks and the pyramid crumbles.
- Keys: digits, Backspace, Enter, arrows.
About the game
Sum Pyramid is a calm number puzzle built on the classic classroom number wall. The rule is simple: every brick is the sum of the two bricks it sits on. Fill the bottom row and the rest follows, but these pyramids rarely give you the bottom row. A few numbers are scattered around, and you have to find where to start.
The first pyramids teach the key move: if you know a brick and one brick under it, subtract to find the other. Then the rules change. From pyramid 13 every brick is the product of the two below, and you divide to work down. From pyramid 19 it is the difference, big minus small, which can go two ways, so you have to check which one fits. The last pyramids hide the middle of the bottom row with nothing next to it known, and the only way in is the middle-brick trick: the top of a three-row block equals the left brick plus twice the middle plus the right brick. Every one of the thirty pyramids has exactly one answer and can be solved one sure step at a time, with no guessing.
Free to play in your browser. No download, no sign-up. Works on phones, tablets and computers. Your progress is saved on this device.
