About this game

This is the game children play with two pens on the back page of a maths book. A football pitch is drawn on squared paper, with a goal at each end and the ball on the centre spot. Red has a red pen and Blue has a blue one.

On your go you draw one line from the ball to a dot next to it: up, down, across or corner to corner. The ball moves to the end of the line. Rings show the dots it can go to. Tap one, or put a finger down near the ball, slide the way you want and let go. The line shows dashed until you lift your finger.

A line can't be drawn twice, and none can go along the edge of the pitch. If the ball lands on a clean dot, it's the other player's go. If it lands on a dot that already has a line, or on the edge, it bounces and you draw again. So early goes are one line long, and later ones zigzag half way down the pitch along lines both players drew earlier.

Red shoots up the page and Blue shoots down. A ball in a goal counts for the player who shoots at it, even if the other player put it there. If you bounce the ball onto a dot with no line left to draw, the other player gets the goal.

The lines of the latest go are marked in yellow highlighter, so you can see what was just drawn. A ring with a dot in it shows where the ball would bounce.

There are two pitches. The full-size one is 8 squares by 10. The small one is 6 by 8 and its games are shorter. A match is one goal or first to 3, with a clean page after each goal.

Two players lay the phone flat between them. Red sits at one end and Blue at the other, and Blue's messages are turned round to face Blue. On your own, you play Red against the computer. On easy it heads for your goal one line at a time and is easy to lead into a corner. On hard it works out whole chains of bounces and what you could draw in reply.

Good for

• Two children sharing one phone or tablet
• Wet play, when the class can't go outside
• Thinking a few moves ahead: each line you draw is one the other player can bounce off later