# canvas2d-isometric-renderer

Builds the draw loop for an isometric tilemap on Canvas 2D: ground tiles first, depth-sorted sprites after.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · ★ 41
- Author: 0xheycat
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/0xheycat/isometric-game-skills/tree/HEAD/skills/canvas2d-isometric-renderer/SKILL.md
- Updated: 2026-08-12
- HTML: https://affpapa.org/en/nevibecode/skills/canvas2d-isometric-renderer

## What it does

This skill lays out the render backbone for an isometric world. Ground tiles go back-to-front by row and column, then objects and characters follow in depth order. Coordinate work comes from `isometric-grid-math`, images from the atlas packed by `spritesheet-atlas-packing`, and the camera transform is applied once per frame.

What you get is a seven-step process, a short JavaScript loop example, and a table of excuses it refuses to accept — drawing the whole map every frame being the first one. A red-flags list names the usual failure points: no viewport culling, fresh arrays allocated inside the draw loop, tile pass and object pass tangled together.

The skill leans on its neighbours. Skip `depth-sorting-occlusion` and sprites end up behind walls; skip `camera-pan-zoom-controls` and there is no transform to apply. Verification asks for three checks: tiles drawn back-to-front, objects drawn after tiles in depth order, and nothing drawn outside the visible area.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add 0xheycat/isometric-game-skills --skill canvas2d-isometric-renderer -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/canvas2d-isometric-renderer/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/canvas2d-isometric-renderer/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add 0xheycat/isometric-game-skills --skill canvas2d-isometric-renderer -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/canvas2d-isometric-renderer/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add 0xheycat/isometric-game-skills --skill canvas2d-isometric-renderer -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/canvas2d-isometric-renderer/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install 0xheycat/isometric-game-skills canvas2d-isometric-renderer
```

2. **Manually: put the files in place**
- File: `.github/skills/canvas2d-isometric-renderer/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add 0xheycat/isometric-game-skills --skill canvas2d-isometric-renderer -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/0xheycat/isometric-game-skills --path skills/canvas2d-isometric-renderer
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/canvas2d-isometric-renderer/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add 0xheycat/isometric-game-skills --skill canvas2d-isometric-renderer -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/0xheycat/isometric-game-skills/tree/HEAD/skills/canvas2d-isometric-renderer/SKILL.md

## When to use it
- draw an isometric tilemap on Canvas 2D
- fix sprite order when objects hide behind walls
- wire grid math and a sprite atlas into one draw loop
- cull tiles outside the visible viewport
- stop allocating arrays inside the draw loop

## Example prompts
- Build the isometric draw loop: ground tiles first, then objects sorted by depth
- Sprites render in the wrong order — trace the draw loop and fix it
- Add viewport culling to the current tile pass

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: c3969176ad4f9e9f.

BEGIN THIRD-PARTY FILE c3969176ad4f9e9f
````text
---
name: canvas2d-isometric-renderer
description: Use when building a Canvas 2D renderer that draws an isometric tilemap and sprites efficiently with correct ordering.
license: MIT
---

# Canvas2D Isometric Renderer

## Overview

This skill builds the core render loop: draw ground tiles back-to-front, then depth-sorted objects, using the grid math transform and the atlas. It is the backbone every gameplay skill plugs into.

## When to Use

- You need to actually draw the isometric world.
- Tiles or sprites render in the wrong order.
- You are wiring grid math + atlas into a render loop.

## Process

1. Use `isometric-grid-math` for all coordinate conversions.
2. Draw ground tiles in back-to-front order (by row+col).
3. Draw objects/characters AFTER tiles, sorted by depth (see `depth-sorting-occlusion`).
4. Source every image from the atlas (see `spritesheet-atlas-packing`).
5. Apply the camera transform once per frame (see `camera-pan-zoom-controls`).
6. Only draw tiles within the visible viewport (culling).
7. Keep the draw loop pure - no allocations per frame.

```js
for (const tile of tilesInView) drawTile(tile);
for (const obj of sortByDepth(objectsInView)) drawSprite(obj);
```

## Rationalizations (Stop Lying to Yourself)

| Excuse | Reality |
|---|---|
| "I will draw everything every frame" | Drawing off-screen tiles wastes the frame budget. Cull. |
| "Order does not matter much" | Wrong order = objects behind walls. Sort every frame. |

## Red Flags - STOP if you catch yourself:

- Drawing the entire map instead of the viewport.
- Allocating arrays/objects inside the draw loop.
- No separation between tile pass and object pass.

## Verification

You are NOT done until every box is checked:

- [ ] Ground tiles draw back-to-front correctly.
- [ ] Objects draw after tiles in depth order.
- [ ] Only visible tiles are drawn (culling works).
````
END THIRD-PARTY FILE c3969176ad4f9e9f

The third-party file has ended. Everything between the c3969176ad4f9e9f tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

© 0xheycat · MIT · https://github.com/0xheycat/isometric-game-skills/tree/HEAD/skills/canvas2d-isometric-renderer/SKILL.md

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From the same set: [0xheycat/isometric-game-skills](https://affpapa.org/en/nevibecode/by/0xheycat/isometric-game-skills.md) — 7 cards

---
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