How to Make an Arena Fighter with AI: A Small 2D Game Recipe

What you will build

One tiny platform arena, one original player fighter versus one basic AI, move, jump, one light attack, simple damage/knockout and restart. No roster, heavy/special moves or online play. Start with original shapes, readable health and keyboard plus touch controls. The starting prompt requests complete HTML, JavaScript and Canvas in one file; review and test the AI’s result.

Five build stages

1. Make movement readable

   Start with one self-contained HTML/Canvas file, a floor and two platforms. Draw original shapes; add left/right movement and jump. Use elapsed time, grounded checks and one collision owner. Expected result: the fighter lands reliably without falling through the floor.

2. Prove one attack

   Add one light attack with a visible wind-up, active hit window and cooldown. Give each attack an identifier so one swing cannot hit the same target every frame. Keep the hurtbox separate from the artwork. Expected result: one accepted hit reduces health once.

3. Add one basic opponent

   Use a second original shape. Give it a simple approach/attack/recovery state and safe starting distance. Keep it inside the same arena; do not install a pathfinder for an open floor. Expected result: the opponent can act, take damage and be defeated.

4. Finish the small loop

   Show readable health, clear win/loss and a restart button. Clear held keys on blur and pointer cancellation. Add labelled touch movement/jump/attack controls, pause and safe resize behavior. Expected result: two consecutive rounds start with clean health, positions, timers and input.

5. Test, then make one upgrade

   Test keyboard and actual touch input, miss/hit/cooldown, defeat, pause, resize and repeated restart. Compare one change against the same baseline. Add art, sound or a second arena only after the first loop works. Expected result: one documented improvement with the original controls and outcomes still working.

Choose a compatible route

• Browser first: native HTML/Canvas, keyboard and touch. No package, engine subscription or remote dependency is required by the starting prompt.
• Godot alternative: use native 2D bodies, collision and input in your existing compatible project. Adapt the mechanics rather than pasting JavaScript into GDScript. Follow the tested starter workflow, then test your exact export target.
• Construct alternative: use event sheets in a compatible existing project. Check the current free-edition limits and paid commercial/export terms before choosing it. A paid plan is optional, not required for this browser prototype.

Browser and desktop are first targets. Touch buttons do not establish native Android/iOS support or a measured phone frame rate. Keep the project’s working engine if you already have one.

One upgrade at a time

Troubleshooting

Damage repeats during one swing

Separate attack state from damage application. Track targets hit by the current attack identifier, then clear that set only for the next attack.

The fighter falls through a platform

Check previous/current positions, vertical velocity and platform bounds. Keep one collision owner and test a large frame interval; reduce or subdivide the physics step if needed.

The game keeps moving after release

Clear held input on blur, visibility change, pointercancel and lostpointercapture. A pointer leaving a touch button must not leave movement stuck.

The opponent attacks constantly

Give approach, wind-up, active and recovery distinct states. Test with a stationary player before increasing speed or adding opponents.

The AI returns fragments or asks many questions

Paste the exact Quick Prompt into a fresh chat. Request the complete runnable HTML file now, then fix one redacted error at a time while preserving working code.

Desktop, mobile and performance checks

Run two full rounds on the actual desktop browser and a physical phone. Test every labelled action, multi-touch release/cancellation, keyboard focus, portrait/landscape resize, pause and restart. Make the controls usable without colour alone; provide readable status outside the canvas.

Use one frame owner, bounded elapsed-time physics and a small fixed opponent count. Profile the actual device before adding particles or sounds. No device-FPS, provider-generated build or assistive-technology result is claimed here.

Original sources

• MDN: Canvas tutorial ↗
• MDN: Pointer Events ↗
• MDN: animation loop ↗
• BINX Brawl: existing playable example ↗