Scrap Mechanic Blueprint Skill

Quick Start

1. Ask user for game install path (usually D:\SteamLibrary\steamapps\common\Scrap Mechanic\ or C:\Program Files (x86)\Steam\steamapps\common\Scrap Mechanic\)
2. Only modify existing blueprints — never create new UUID. Game can't find new blueprints. User tells you which blueprint name/ID to overwrite.
3. Blueprint save path: %APPDATA%\Axolot Games\Scrap Mechanic\User\User_*\Blueprints\\blueprint.json

Parts Database

Load references/parts-database.json for 170+ parts with UUIDs, sizes. Load references/block-types.md for zaxis/bounds rules.

Blueprint JSON Format (v4)

{
  "bodies": [{"childs": [...]}],
  "joints": [...],  // optional
  "version": 4
}

Each child: {"color":"HEX","controller":{...},"pos":{"x":x,"y":y,"z":z},"shapeId":"uuid","xaxis":1,"zaxis":-2}

Block Type Differences (CRITICAL)

Never mix zaxis values between types.

controllers (logic wiring)

• controllers: [{"id":X}] = this component's output goes TO component X
• controllers: null = endpoint (light, no forwarding)
• IDs start at 1; 0 is reserved

Logic Gate Modes

Key Rules (Game Verified)

1. Signal has NO loss — fan-out is unlimited, no buffers needed
2. 1 tick delay per hop — only propagation cost
3. Lights only accept ONE input — need OR gate to combine multiple sources
4. Blocks must be adjacent — floating blocks split into separate pieces
5. Bearing+board+wheel form rigid triangle — can't change relative positions
6. Wheels: small d=3+margin*2≈4 effective, spacing ≥4

Vehicle Building (zaxis=-2 orientation)

Board at z=2, xaxis=1, zaxis=-2
Bottom wheels: pos(board_x-1, -1, 4), zaxis=-2
Top wheels: pos(board_x+2, 3, 4), zaxis=2
Bearing joint: posA=posB=(board_x, -2, 2) bottom / (board_x, 3, 2) top

Digital Circuits (Game Verified)

Core Circuits

• 1-tick pulse gen: AND→NAND→AND feedback
• T flip-flop: edge detector(AND+NAND)→XOR↺self
• OR self-latch: OR↺self, 1-tick pulse→permanent ON
• 3-OR ring oscillator: odd ORs = stable oscillator
• Ripple counter: shared 1tick pulse→XOR chain with carry ANDs
• Simplified counter: pulse width < chain length prevents ripple, saves NANDs

Display Decoder

Counter bits → NAND inverters(single input=~X) → 
  Value-detecting AND gates(one per value) → Pixel-collecting OR gates → Lights

Each light has exactly ONE OR gate as input. OR gate collects from all value-ANDs where pixel should be ON.

Tools

Use scripts/blueprint_builder.py for programmatic blueprint generation. Key API:

• Blueprint(name, version=4) — create blueprint
• .block/shape, x, y, z) — add static block (platform connector)
• .metal(x, y, z, w, h, d) — add metal block with bounds
• .cube/hollow_cube/sphere/cylinder(...) — geometry
• .part/shape, x, y, z, mode, controllers) — interactive component
• .gate/type, x, y, z, inputs) — logic gate shortcut
• .add_wheel(side, body, board_x, board_y) — vehicle wheel with bearing
• .save_to(target_dir) — save to existing blueprint directory