Origami: water bomb

1. Cut out the square. Colour it first if you like.
2. Fold the square diagonally in half, corner to corner, and unfold. Do the same with the other two corners. You'll now see a cross.
3. Turn the paper over. Fold it straight in half, edge to edge, and unfold. Do the same the other way too.
4. Turn it back again. Push the left and right sides in at the middle and let the top drop down. Press flat: you have a triangle with two flaps in front and two behind.
5. Fold the two bottom corners of the front flaps up to the top point. Turn over and do the same on the back: a diamond.
6. Fold the left and right points of the diamond to the middle. Do the same on the back.
7. There are now loose points at the top. Fold them down until they touch the middle.
8. Tuck those little triangles into the pockets of the triangles you just folded to the middle. Turn over and do these last two steps on the back too.
9. There's a little hole at the bottom. Blow into it hard: the water bomb puffs up into a cube! Gently push the corners straight.

Thin paper works best: ordinary printer paper or origami paper, not thick paper.