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Weight Pond Tune the frog's weights. Find out why one neuron isn't enough.
A frog decides whether to jump with one sum: two weights and a bias. Drag the sliders until it lands on every lily pad with a fly, or press Let it learn and watch it fix its own mistakes. The last two ponds can't be solved by any single frog — you'll need two, and that's why neural networks have layers.
1–2 players · ~10–14 + parents · ~15 min · one screen
Frank Rosenblatt — key figures →
Play in your browser
Free, no login. Nothing you do in the game leaves your device. Works on a laptop, tablet, or phone.
Good to know
Plays in any browser on one screen. No account, and nothing you do in the game leaves your device. The one-page guide prints on plain paper and has an unplugged version for a class without screens.
How to play
A frog decides whether to jump with one sum: weight × left-right + weight × up-down + bias. If the total is above zero, it jumps. Drag the sliders until it jumps on every lily pad with a fly and none of the stones. Six ponds. The last two can't be done with one frog.
How to play
- Each dot is a lily pad. Amber pads have a fly. Grey ones are stones.
- The line is where the frog's sum is exactly zero. On the shaded side the sum is above zero, so the frog jumps.
- Drag weight 1 and weight 2 to turn the line. Drag the bias to slide it. Get every dot right to clear the pond.
- Stuck? Press Let it learn. The frog finds one dot it got wrong and nudges its numbers toward fixing it. Press again to watch it learn.
What the frog teaches
- A neuron is a weighted sum plus a threshold. Nothing more mysterious than that.
- Weights are what a neural network learns. Training means nudging them after every mistake.
- Some patterns can't be split by one line. Ponds 5 and 6 need two neurons working together: a layer.
- Bigger networks are the same idea stacked up: millions of weights, all nudged by mistakes.
No screens? Play it unplugged
- No screens? Draw 10 dots on graph paper, some circled. Students take turns drawing one straight line that separates circled from plain.
- Then draw a stripe of circled dots across the middle. Can one line do it? How many lines does it take?
- Ask: if a computer only had straight lines, how would it learn a curvy pattern? (Answer: lots of lines, combined.)
Downloads
Grown-up guide
Plain paper · 1 page · 8.5 × 11
How to play, what it teaches, the six ponds, and a no-screens version with graph paper.
Guide preview
One page for grown-ups and classrooms: what it teaches, plus a version with no screens.
On a phone, open the PDF in a new tab — in-page previews are unreliable in mobile Safari.
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