SKILL.md
App icon generation
Platform requirements (non-negotiable)
| Platform | Size/format | Transparency | Safe zone |
|---|---|---|---|
| iOS App Store | 1024×1024 PNG, no alpha | opaque | squircle mask applied by OS; keep subject in 824px center |
| iOS device | 180, 167, 152, 120, 87, 80, 76, 60, 58, 40, 29, 20 (@1x, @2x, @3x) | opaque | same |
| iOS 18 dark / tinted | Icon Composer layered source | per-layer | same |
| Android adaptive | 108 dp foreground + 108 dp background; 72 dp visible safe zone | FG yes / BG no | 72 dp of 108 dp |
| Android 13 monochrome | themed drawable | yes | same |
| Google Play | 512×512 PNG, no alpha | opaque | — |
| PWA | 192, 512 any; 512 maskable |
maskable: opaque + 80% safe zone |
80% of 512 for maskable |
| visionOS | 3× 1024² PNGs (parallax layers) | per-layer | — |
Generation — mark, then pack
Never generate per-platform. Always: one 1024² RGBA master → deterministic fan-out.
- Route the mark generation (see
skills/logo/SKILL.md) — no text; subject-only. - Matte with BiRefNet if the chosen provider returned opaque.
- Deterministic export via
pipeline/export.ts::exportAppIconBundle(puresharp— no external CLI dependency):
- iOS: AppIcon.appiconset/Contents.json + every required PNG (iPhone/iPad/Mac/Watch/marketing). 1024 marketing variant flattened onto brand primary color (App Store rejects alpha). iOS 18 dark/tinted appearances emitted when ios18appearances: true. - Android: mipmap-{mdpi,hdpi,xhdpi,xxhdpi,xxxhdpi}/iclauncher.png + mipmap-anydpi-v26/iclauncher.xml pointing to iclauncherforeground + iclauncherbackground + iclaunchermonochrome (foreground-derived via greyscale+threshold; the final themed-icon result should still be audited manually for complex marks). - PWA: 192.png, 512.png, 512-maskable.png (80% safe-zone padding) + manifest-snippet.json. - visionOS: 1024² master.png + a README describing the 3-layer parallax split that Xcode's Reality Composer Pro or a manual Photoshop step produces. - Favicon bonus: .ico (16/32/48 multi-res) via optional png-to-ico; falls back to separate PNGs with a warning if the dep is absent.
Prompt scaffold
A [flat vector | isometric 3D | glyph | soft gradient] app icon representing [SUBJECT, concrete noun phrase].
Bold, memorable silhouette. High contrast.
Subject fills 70-80% of frame, centered.
No text, no labels, no wordmark.
Palette: [#primary, #secondary, #accent].
Solid pure white background.
1:1 square, 1024x1024.For platform styling: iOS-style rounded square backdrop or Android-style adaptive foreground on transparent can be added to steer, but the mark should be subject-only — backdrop is applied deterministically in export.
Android 13 monochrome derivation
Heuristic (see Open Question G11 in SYNTHESIS.md): sharp(foreground).greyscale().threshold(128).tint('#000'). Works for bold single-subject marks; audit visually for complex marks.
Validation
- 1024 marketing variant: opaque, dimensions exact, file <1MB.
- Android foreground: tight-bbox inside 72dp of 108dp.
- PWA maskable: subject inside 80% center circle.
- Contrast at 16×16 (renders to "favicon-ish" size): WCAG AA vs both white and dark card.
- No text detected by OCR (app icons must be text-free).
Output
app-icon/
├── master.png # 1024² RGBA
├── ios/AppIcon.appiconset/ # Contents.json + all sizes
├── ios/AppIcon-1024-opaque.png # App Store marketing
├── android/mipmap-*/ic_launcher.png
├── android/mipmap-anydpi-v26/ic_launcher.xml
├── android/drawable/ic_launcher_{foreground,background,monochrome}.png
├── pwa/{192,512,512-maskable}.png
├── pwa/manifest-snippet.json
├── visionos/{front,middle,back}.png # if parallax
└── meta.json