platform tile assets

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Thumbnail output is two separate files, never composite

The thumbnail tool outputs background.png and foreground.png as separate files, never composited together. Stake's builder layers them itself. The script also generates background_master.png and foreground_master.png at full resolution. These must be uploaded to Stake's builder separately.

Background and foreground are a matched pair

The background and foreground tiles are generated as a matched pair with the same art style, palette, and lighting via a shared --style clause. When Stake stacks them, they read as one cohesive picture. The background is kept with its lower-centre open and auto brightness-normalised to mid.

Foreground must be a single hero character, fully visible

The foreground is exactly ONE key character rendered as a transparent cutout with green chroma removed. It must be a head-and-shoulders portrait framing that is big and dominant, with the WHOLE character staying inside the frame including the entire crown/hat with all its points intact, never cropped. A margin of empty space must surround the character on every side with clear breathing room above the head.

Aspect ratio is always 9:16 portrait

Thumbnail aspect is always 9:16 (tall portrait) for both background and foreground. The script forces aspect="9:16" and this must never be overridden to a square or landscape tile.

Bottom third is title-safe zone, keep it clean

The bottom third (lower ~40%) of the tile is the title-safe zone where Stake bakes the game title and gradient. The face goes in the upper 60%. The bottom third must be a plain, uncluttered area with bare shoulders, chest, or cloak. Hands, weapons, sceptres, wands, gems and fine detail must stay above the chest and out of the lower third to avoid colliding with title text.

Foreground character looks straight at camera

The character in the foreground must look right at the viewer with eye contact and attitude. A signature prop may be foreshortened toward the camera for depth but must be framed in the upper or middle section, never thrust down into the title zone. The framing should have dynamic hero energy, never a flat mugshot or cluttered lower third.

No text, words, numbers, or multipliers in art

Neither background nor foreground may contain text, words, numbers, multipliers, tags, labels, signage like SALOON, mug labels like DECAF, or price tags like LIQUIDATED. The script appends hard negatives to kill such elements. Stake adds all required text itself.

No gradient, no title bake in source assets

The source thumbnail files must never include a gradient or game title. Stake's builder adds the gradient and game title itself when compositing the layers.

Chroma key default is cyan, pick a key the character does not contain

The default chroma key is cyan (--chroma cyan). Select a key colour that the character does NOT contain. If the mascot is green, do not use --chroma green or it will vanish; use cyan (default) or magenta instead. If it has cyan in it, use magenta. The script auto-appends "on solid pure <colour> background" to the prompt; do not add your own chroma clause.

Thumbgen.py script usage and parameters

The thumbnail generation script is at ~/.claude/skills/thumbnail/scripts/thumbgen.py. Basic usage: python3 thumbgen.py --game-dir "path" --style "art style description" --bg-prompt "environmental scene" --fg-prompt "one hero character" on solid pure green background. Flags: --max-px 1000 (default, long side capped), --bg-quality (low|medium|high), --fg-quality (low|medium|high), --chroma cyan|green|magenta (default cyan). The --style is injected into both prompts to ensure matched-pair cohesion.

Background quality is medium, foreground is high

Backgrounds are generated at medium quality (~$0.03 @1K) via image-gen at apimart. Foregrounds are generated at high quality. Both are generated at 1K resolution with long side capped via --max-px (default 1000px) and full-res masters are saved.

Background must keep lower-centre open

The background environmental scene must keep its lower-centre area open and unobstructed. This allows the game title and gradient overlay to sit cleanly over it without visual collision.

Transparent margin padding for foreground safety

The script automatically re-pads a ~6% transparent margin (_margin) around the foreground subject to ensure that a character drawn flush to the edge never ends up cut by the frame. However, the prompt must still ask for the full character to be visible within the frame.

Matched-pair cohesion via shared style clause

The --style parameter is shared between background and foreground prompts and controls the cohesion of the matched pair. Example style: "Hacksaw Gaming 2D vector cartoon, thick black outline, milky charming flat shading, <theme palette>, single soft light source". This style is injected into BOTH prompts to ensure the two tiles read as one picture when stacked.

Output directory default is game-dir/thumbnail/

The default output directory for generated files is <game-dir>/thumbnail/. Files are written as background.png, background.webp, foreground.png, background_master.png, and foreground_master.png in this location.

Trigger phrases for thumbnail generation

The thumbnail skill is triggered by the phrases "/thumbnail", "сделай thumbnail", "game tile", "Stake тайл", and "превью игры".

What is a matched background-foreground pair in platform game assets and why do we generate them together

A matched background-foreground pair in platform game assets consists of two separate files: a background environmental scene and a foreground hero character portrait. They are generated together with the same art style, palette, and lighting via a shared --style clause so that when Stake's builder stacks them, they read as one cohesive picture. The background is brightness-normalised to mid and kept with lower-centre open, while the foreground is a single transparent-cutout character with chroma removed. They function as source assets that Stake composes itself with gradient and title overlay.

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