# Optimization

> Optimization techniques for Nethercore WASM games. Covers WASM binary size reduction (LTO, wasm-opt), texture and mesh compression, audio optimization, and state size minimization. Use when a ROM exceeds size limits or when reducing build output size.

- Skill: `nethercore-systems/optimization` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add nethercore-systems/optimization`
- Raw SKILL.md: https://api.skillmd.com/api/skills/nethercore-systems/optimization/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- License: Apache-2.0
- Author: nethercore-systems (https://skillmd.com/u/nethercore-systems)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/nethercore-systems/optimization

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# Nethercore Optimization

Measure first; use existing build/platform features before adding tooling. Keep simulation and asset correctness while reducing the resource actually over budget.

## WASM

```toml
[profile.release]
lto = true
opt-level = "z"
codegen-units = 1
panic = "abort"
```

Compare size and runtime performance; `"s"` may be better for a particular game. Strip symbols only when debugging requirements permit. `wasm-opt` is optional, not a dependency to install blindly. If used, optimize the actual manifest-selected WASM before `nether pack` and rerun the cart; optimizing a loose file after packing changes nothing in the cart.

## Textures and meshes

ZX RGBA8/BC7 selection is explicit `[game].compress_textures`, not automatically all textures. BC7 uses 16 bytes per 4x4 block, approximately 1 byte/pixel on aligned dimensions, not 0.5. Keep atlas padding/alpha and inspect actual VRAM.

Distinguish float input vertices from packed ROM/GPU vertices. Use `zx-common`'s format/stride functions, not a fixed universal table. Drop attributes only when the render mode/material/normal mapping/skinning permits it. Preserve complete intended geometry through the first-mesh/primitive GLB importer.

## Audio and state

Target PCM is 22050 Hz mono i16; raw WAV currently needs to arrive in that format. XM/IT pattern data plus shared samples can be compact, but there is no guaranteed percentage saving or fixed bytes-per-second for a tracker module.

Use bounded arrays when they fit. A `Vec` is not inherently non-deterministic if allocator/data/RNG state are snapshotted and iteration is stable. Smaller integer fields need explicit range/scale/overflow policy; `i16` alone does not define fixed-point math. Do not reduce numeric accuracy merely to satisfy an arbitrary state-size target.

See [optimization techniques](references/optimization-techniques.md) for the verification sequence.