Visual assets

Foray ships its own generated pixel art: a single sprite-sheet PNG plus an atlas JSON, consumed by the browser replay renderer. This page is the art specification: the dimensions, the required frames, the palette, and the atlas format, so the assets can be generated, reviewed, and regenerated against a fixed target. The art is original throughout, on an ant-colony raiding theme.

The look is a top-down 16 px pixel-art colony. A packed sheet keeps the case to two committed files, draws as a single texture, and recolours per team by palette swap rather than by shipping duplicate art. A fixed 16 px grid matches the discrete, tile-locked board exactly, at one sprite cell per maze tile.

The renderer holds no game logic. It maps a reconstructed tick’s entities onto sprite cells, and the rules stay in foray-core.

Files and layout

The assets live with the case, beside the renderer:

test-cases/adversarial/easy/foray/v1.0.0/replay/
  index.html          # the [replay] renderer entry
  renderer.mjs        # canvas drawing: interpolation, walk cycles, autotiling
  assets/
    gen-sheet.mjs     # the packer: composes source art -> sheet.png/json
    sheet.png         # the packed sprite sheet (RGBA PNG)
    sheet.json        # the atlas: frames + anims + wall_tiles + border_tiles
    palette.json      # named color slots + per-team ramps
    source/           # committed finished per-asset art the packer composes in

sheet.png is one PNG with cells on a 16 px grid, frames packed from the top left. It is plain RGBA, because the renderer’s per-team recolour matches the neutral ramp by colour value rather than through an indexed palette.

sheet.json is the atlas. Named frames map to pixel rectangles, and it carries the animations the renderer plays as an agent crosses a tile and the autotile maps it selects board tiles from:

{
  "cell": 16,
  "frames": {
    "soldier_s_0": { "x": 0, "y": 0, "w": 16, "h": 16 },
    "raider_e_2": { "x": 96, "y": 16, "w": 16, "h": 16 },
    "seed": { "x": 16, "y": 48, "w": 16, "h": 16 },
    "wall_5": { "x": 0, "y": 80, "w": 16, "h": 16 },
    "floor": { "x": 48, "y": 80, "w": 16, "h": 16 },
  },
  "anims": {
    // One ordered walk cycle per role and facing. The renderer ties the phase to
    // motion and falls back to `fps` when free-running.
    "soldier_walk_s": {
      "frames": ["soldier_s_0", "soldier_s_1", "soldier_s_2", "soldier_s_3"],
      "fps": 8,
    },
    "raider_laden_walk_s": { "frames": ["raider_laden_s_0"], "fps": 6 },
  },
  "wall_tiles": { "0": "wall_0", "5": "wall_5", "15": "wall_15" },
  "border_tiles": {
    "cap_top": "border_cap_top",
    "mid": "border_mid",
    "cap_bottom": "border_cap_bottom",
  },
}

Required frames

Team colour comes from the palette swap, so each agent and nest frame is authored once in a neutral base ramp and tinted Red or Blue at draw time. The moving casts are walk cycles: four frames per facing, named <role>_<facing>_<step> and grouped into the atlas’s anims, which the renderer cycles as the agent crosses a tile.

Group	Frames	Notes
Soldier	soldier_{s,n,w,e}_{0..3} (16)	Mandibled, angular silhouette; a 4-step walk cycle per facing, grouped as anims.soldier_walk_{s,n,w,e}.
Raider, empty	raider_{s,n,w,e}_{0..3} (16)	Lighter, leaner silhouette; 4-step walk cycle per facing, grouped as anims.raider_walk_*.
Raider, laden	raider_laden_{s,n,w,e}_{0..3} (16)	The same cycles carrying a seed, the carry-weight tell, grouped as anims.raider_laden_walk_*.
Seed cache	seed	The ordinary scorable resource, worth 1.
Large seed	large_seed	Worth and weighing three ordinary seeds. It is the only fixture that moves, so it is drawn per frame from the snapshot’s large_seeds. Its drift step is a discrete hop, so it is drawn unsmoothed.
Royal jelly	jelly_active, jelly_spent	Active is a glowing node; spent is the dimmed husk after it is eaten. A node regrows at the same tile, and the renderer derives “spent” as any jelly tile absent from the frame’s active jelly list.
Maze walls	wall_{0..15}	A 4-neighbour autotile set. The frame index is the N=1, E=2, S=4, W=8 connection bitmask, mapped in wall_tiles, so walls render as a connected maze.
Boundary seam	border_{cap_top,mid,cap_bottom}	The no-man’s-land divider down the middle, in border_tiles, capped top and bottom with a tileable middle.
Floor	floor	Dug-tunnel ground the maze sits on.
Nest	nest	One frame, tinted per team, marking each spawn.

Immunity has no sheet frame. The renderer draws a breathing additive cyan aura procedurally over any agent with immune_ticks > 0, pulsed by the tick clock. An immune soldier is reachable, because a raider that eats jelly and runs home keeps its window, so the aura applies to either role.

Facing is decorative, since the rules are direction-agnostic, and the renderer falls back to a single static frame name when a walk animation is absent, so the contract tolerates a partial set.

Palette and recolour

palette.json defines named colour slots and the per-team ramps that fill them, so the two colonies are one art set rendered twice:

{
  "slots": ["body_dark", "body_mid", "body_light", "accent", "carried_seed"],
  "shared": {
    "soil_dark": "#241a12",
    "soil_mid": "#3a2a1c",
    "floor": "#1b1410",
    "border": "#4a3f2a",
    "seed": "#e8c14a",
    "jelly": "#7be0a0",
    "jelly_spent": "#3c5a47",
    "carried_seed": "#ffd964",
  },
  "teams": {
    "red": {
      "body_dark": "#5a1410",
      "body_mid": "#a83228",
      "body_light": "#e8635a",
      "accent": "#ffb0a0",
    },
    "blue": {
      "body_dark": "#0f2a5a",
      "body_mid": "#2a5aa8",
      "body_light": "#5a8fe8",
      "accent": "#a0c8ff",
    },
  },
}

At draw time the renderer bakes one tinted copy of the sheet per team by matching the four neutral grey ramp values by colour and rewriting them to that team’s ramp, so the swap needs an RGBA sheet rather than an indexed palette. Seeds, jelly, and the soil tiles use the shared ramp and avoid the four neutral greys, so the value match leaves them untouched. The board therefore reads as earthy soil and dug tunnels with the two colonies as the only saturated colour, and a laden raider’s carried seed stays legible against either colony.

Generation

Every frame is the output of an asset-generation case drawn against its own brief:

Asset	Case
Nest	foray-nest (single sprite)
Seed cache	foray-seed (single sprite)
Large seed	foray-large-seed (single sprite)
Royal jelly, active and spent	foray-jelly (2-frame sheet)
Soldier walk cycles	foray-soldier (16-frame sheet)
Raider walk cycles, empty and laden	foray-raider (32-frame sheet)
Maze wall autotile, boundary, and floor	foray-walls (20-frame sheet)

A run’s regenerated frames are committed under replay/assets/source/, named for the atlas frame they fill, with the frame-index mapping recorded in source/README.md. A regeneration is an ordinary diff a reviewer can eyeball, either per frame or on the packed sheet.png.

The committed Node packer replay/assets/gen-sheet.mjs composes the sheet. Run node gen-sheet.mjs from replay/assets/. For every frame in the frame list it blits the finished art from source/<name>.png when present and otherwise draws a structured placeholder glyph, then writes the RGBA sheet.png and the sheet.json atlas in sync with palette.json. Re-run the packer whenever source/, the frame list, or the palette changes.