Bridge Builders

Bridge Builders is a gentle measuring puzzle for young children. Three ducklings want to cross a stream to their mum. Wooden stumps stand in the water and a ruler runs along the gap. Lay planks from the kit so that both ends of every plank rest on a stump or the bank, and when the gap is covered the ducklings waddle across, each plank dipping and singing under their feet.

Pick a plank (each shows how long it is), slide it along the stream and put it down. On a phone or tablet, tap a plank in the kit and then tap the stream; tap a plank on the bridge to pick it up again. On a computer, Up and Down pick a plank, Left and Right slide it, Space puts it down and Shift picks the last one back up. A plank with nothing under one end tips into the water with a splash, and the game says which end needed a stump.

Four streams of three bridges: later streams have stumps that lead nowhere, spare planks, and flat stones that need a post first. Three acorns are your tries, and everyone gets the same bridges each day. Calm stream has no tries to lose and shows green and red at the plank's ends while you aim.