Cannon: a projectile physics game

What you’ll get

A cannon, a target, angle and speed sliders, and a dotted trajectory line. After each shot you see the height, distance and flight time. Hit the target and it moves. Press “Play the example” above — Gemini made it from the prompt below.

Steps

1. Open gemini.google.com. If you’re under 13, do it together with a parent, on their device.

2. Copy the whole prompt and send it:

   Make a "Cannon" lab in one HTML file. Don't load anything from the internet: no Tailwind, CDN, fonts, images or libraries — only your own CSS and JavaScript inside the file. Don't save anything in browser storage. On a canvas, put a cannon on the left and a target at a random distance on the right. Add sliders for angle (0–90°) and speed, and a "Fire!" button. Show with a dotted line where the cannonball will go. The cannonball flies along a real parabola (Y axis pointing up), with an "air resistance" switch. After each shot, show the height, distance and flight time. Add a planet choice: Earth, Moon, Mars. Count how many shots it took to hit the target; after a hit, the target moves. Everything should look good on a phone. Show the result in Canvas.
   

3. Wait about a minute, press Preview and try every button and slider.

4. Check the AI (see the question above).

5. Press Download (sometimes it’s under the Export menu). The file opens in any browser. Show it off in class!

Change the prompt

Before sending, swap a few words to make your own version. Change only the words, and keep the rules about the internet and Canvas.

• “Earth, Moon, Mars” → “Earth, Jupiter, Moon”
• “cannon” → “catapult”, “cannonball” → “watermelon”

If it doesn’t work

• The AI says it changed everything, but the result looks the same? Write: Nothing changed. Show the updated version in Canvas.
• No Preview button? Write: Show the result in Canvas.
• The cannonball flies down instead of up? Write: “The ball flies into the ground. The Y axis must point up. Fix it.”