Retrodiffusion

Retro Diffusion — True Pixel Art Generation

Generate authentic pixel art sprites, tilesets, and animations from text prompts or reference images using the Retro Diffusion API. Output is true pixel art (clean integer-pixel grids, limited palettes), not blurry diffusion-model output downscaled into pixels — making it the best AI option for shippable 2D game art and fast prototyping.

Paid service. Retro Diffusion requires an account at https://www.retrodiffusion.ai and an API key with credits. Always tell the user this requires a paid Retro Diffusion account before generating anything, and confirm they understand each call deducts from their balance.

Reference Files

When to Use

• Quick prototypes — generate dozens of unique sprites in a minute instead of hand-coding 16×16 arrays
• Polish pass on a working game — replace placeholder shapes with cohesive pixel art that already matches a chosen style
• Tilesets — wang-style ground/wall sets without manually drawing every transition tile
• Sprite animations — walk cycles, idle bobs, attacks delivered as transparent GIFs or spritesheets

Choose this over `add-assets` (code-only pixel art) when: the user wants AI-generated art, has a Retro Diffusion key, or the game needs more visual variety than hand-coded matrices can deliver in a reasonable time. The two skills compose well — Retro Diffusion for hero sprites/tilesets, code-only matrices as a free fallback for quick filler.

Do NOT use this for: 3D models (use meshyai), 3D worlds (use worldlabs), audio (use game-audio), or when the user explicitly wants the all-code procedural pixel art approach (use add-assets).

Authentication

Before prompting the user, check if the key already exists:

test -f .env && grep -q '^RETRODIFFUSION_API_KEY=.' .env && echo "found"

If found, export it with set -a; . .env; set +a and skip the prompt.

If the key is not set, ask the user immediately and explain the cost model:

I'll generate true pixel art with Retro Diffusion — the best dedicated pixel art model for shippable game sprites. Heads up: this is a paid service. You'll need a Retro Diffusion account with credits. Each image typically costs between $0.015 (RD_FAST) and $0.18 (RD_PRO). Get a key in 60 seconds: 1. Sign up at https://www.retrodiffusion.ai 2. Buy credits (smallest pack is fine for prototyping) 3. Account → API → Generate API key Paste your key like: RETRODIFFUSION_API_KEY=rdpk-... (It will be saved to .env and redacted from this conversation.) Or type "skip" to fall back to free hand-coded pixel art via /add-assets.

If the user provides a key, save it to .env and use it via set -a; . .env; set +a && node scripts/retrodiffusion-generate.mjs ....

If the user skips, stop and hand off to `/add-assets` — do not silently degrade to a different art style without telling them.

CLI Script — scripts/retrodiffusion-generate.mjs

Zero-dependency Node.js script. Handles all six modes: generate, img2img, animate, tileset, edit, and balance.

Generate (text-to-pixel-art)

# Single 64×64 sprite, RD_FAST (cheapest)
RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode generate \
  --prompt "a cute green slime with big eyes" \
  --model RD_FAST --style retro \
  --width 64 --height 64 \
  --output public/assets/sprites/ --slug slime

# Higher quality with RD_PRO (flat $0.18, supports up to 256×256)
RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode generate \
  --prompt "a heroic knight, full body, side view" \
  --model RD_PRO --style fantasy \
  --width 128 --height 128 \
  --output public/assets/sprites/ --slug knight

# Transparent background for game sprites
RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode generate --prompt "a treasure chest, closed" \
  --model RD_FAST --style game-asset \
  --width 64 --height 64 --remove-bg \
  --output public/assets/sprites/ --slug chest

# Seamless tiling texture (e.g., grass, water)
RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode generate --prompt "lush grass texture, top down" \
  --model RD_PLUS --style top-down \
  --width 64 --height 64 --tile-x --tile-y \
  --output public/assets/tiles/ --slug grass

# Estimate cost before paying for it
RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode generate --prompt "..." --check-cost

Image-to-Image (refine a reference)

RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode img2img \
  --image ./concept-art/hero-sketch.png \
  --prompt "a heroic knight in shining armor" \
  --model RD_FAST --style retro \
  --width 64 --height 64 --strength 0.75 \
  --output public/assets/sprites/ --slug hero

--strength controls how much the AI deviates from the input (0 = identical, 1 = ignore input). 0.5–0.8 is the useful range.

Animations (walk cycles, idles, attacks)

# Walk cycle — returns spritesheet PNG or transparent GIF (style-dependent)
RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode animate \
  --prompt "a knight walking" \
  --model RD_PRO --style walk-cycle \
  --width 64 --height 64 \
  --output public/assets/sprites/ --slug knight-walk

# Idle bob from an existing character
RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode animate --image public/assets/sprites/knight.png \
  --prompt "knight idle breathing" --style idle \
  --output public/assets/sprites/ --slug knight-idle

Animation styles cost $0.07–$0.25 depending on type. See api-reference.md for the full style list.

Tilesets

# Wang-style tileset (auto-tiling ground/wall sets)
RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode tileset \
  --prompt "stone dungeon floor, mossy" \
  --model RD_PLUS --style wang-tile \
  --width 96 --height 96 \
  --output public/assets/tiles/ --slug dungeon-floor

# Single detailed tile
RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode tileset --prompt "wooden bridge plank" --style single-tile \
  --width 64 --height 64 --output public/assets/tiles/ --slug bridge

Edit (progressive refinement)

Flat $0.06 per edit. Use to tweak a generated sprite without re-rolling from scratch.

RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs \
  --mode edit --image public/assets/sprites/knight.png \
  --prompt "give the knight a red cape" \
  --output public/assets/sprites/ --slug knight-red

Balance check

RETRODIFFUSION_API_KEY=<key> node scripts/retrodiffusion-generate.mjs --mode balance

Model Selection Guide

Default to RD_FAST for prototyping. Upgrade individual hero sprites to RD_PRO when the prototype is shipping.

See api-reference.md for the complete per-model prompt_style list.

Prompt Engineering for Pixel Art

Good prompts are short, specific about silhouette and palette, and call out the perspective: