nextfloor

eye candy mostly. useless mainly.

See it running →

Explore for free. Add a floor with your own Anthropic and fal keys, or use a shared sponsored attempt when the host has enabled the capped allowance.

A generated isometric pixel-art building that grows one floor at a time. Type a theme, and an AI pipeline draws a floor in that theme and stacks it on the tower.

The experiment: can independently generated floor tiles hold a rigid enough visual contract that dozens of them still read as one continuous building?

How a floor is made

1. Theme Interpreter (Claude) turns a theme into a structured floor spec.
2. Art Director (src/lib/building/prompt.ts, plain code) composes that spec with the immutable Building Style Guide into one image prompt.
3. Image generation (fal, Nano Banana) draws the tile from that prompt. Later floors are generated as an edit of the reference tile, which holds the shell far better than conditioning on it. FLUX was tried first and reads the structural prompt as a brief for an architectural render — it returns clean, empty, photoreal CAD cutaways.
4. Validation checks the tile against the contract and retries once.
5. A refusal or a second failure becomes a dead floor — a burnt-out storey rendered in CSS, with the reason on it.

The prompts live in src/lib/prompts/ as markdown, not in code, because they are what gets tuned every session:

• iso-instructions.md — the seed tile, which has nothing to match.
• edit-instructions.md — every later floor, generated as an edit of the reference tile. The reference carries the contract, so this prompt's job is to forbid changing it.
• structure-{floor,roof,basement}.md — the per-kind structural language.

GET /api/prompt?mode=seed|edit renders exactly what would be sent, so the prompt can be read without spending a generation. src/lib/building/styleGuide.ts holds the tile geometry. Changing any of it invalidates the visual compatibility of every floor generated before the change.

Starting tiles

docs/reference/building-spec-sheet.png is the drawn contract: 2048 x 512, 4:1, identical shell on every floor, regular floors open top and bottom, roof closed at the top, basement closed at the bottom.

public/top-floor.png, public/middle-floor.png and public/bottom-floor.png are the static building: roof, reference floor, basement. Seeding imports them instead of generating, and every generated floor is an edit of the middle one. They must share one frame — the import refuses tiles that disagree.

Tiles are transparent PNGs composited over the black page. If a generator bakes the transparency checkerboard in as opaque grey squares, restore real alpha with:

node scripts/dealpha.mjs public/bottom-floor.png

TILE.pitchRatio in src/lib/building/styleGuide.ts is the vertical repeat as a fraction of tile height. It is well below 1 because an isometric frame is much taller than one storey — it also contains the depth receding from the viewer, so stacking tiles a full frame apart leaves a large gap.

Running it

pnpm install
cp .env.example .env.local   # set DATABASE_URL
pnpm dev

Local development uses .env.local keys automatically. Browser keys override them per provider and are never stored server-side. Room hint badges need only Anthropic; creating floors needs Anthropic and fal. Complete BYOK is uncapped.

Production requires PUBLIC_GENERATION=true to expose server keys for anonymous use. PUBLIC_MONTHLY_BUDGET_USD defaults to $10 and accrues in daily portions, with unused daily credit carrying within the month and at most four public floor attempts/day. Keys alone do not opt in; partial production BYOK never silently falls back to public funds. Public access ships disabled. See sponsored generation for setup, accounting behavior, and isolated verification commands.

Tiles are stored in Postgres by default. Set S3_BUCKET (and install @aws-sdk/client-s3) to use an S3-compatible bucket instead.

Controls

Drag to pan, wheel to pan, cmd/ctrl-wheel to zoom at the cursor. The gutter on the left labels each floor and holds its delete button. Floor 1 is the reference tile and cannot be deleted.

Deploying

The Railway service is connected to main: merging deploys. The database is shared, so floors added locally already exist in production and appear as soon as the code catches up.

Sponsorship defaults off. Visitors can always bring their own Anthropic and fal keys.

Conventions

Layout, naming, styling, docs and the issue workflow follow project-standard. Where this repo diverges, the divergence is an open issue rather than a local rule.

Status

Last shipped

• The reference tile is no longer a storey. It is parked out of the numbering, so floor 1 is a slot like any other and the ground floor can be generated.
• Transparency veins repaired in the static tiles, and the prompt now asks for a #222 outline on pure black -- a pure black outline is the same colour as the background to the alpha key, which is what hollowed the lines out.
• The projection angle is stated in the prompt: 1:2.76, about 20 degrees. Floors drifted to textbook 2:1 isometric whenever the model stopped copying, and "keep the camera angle" cannot correct a default it does not name.
• Tiles encode as lossless WebP at ingest, verified pixel-identical. The live building went 116 MB to 52 MB; scripts/optimize-stored-tiles.mjs is the catch-up for anything generated earlier.
• The basement is redrawn from a 2K generation and fitted to the frame.
• Elevator panel: call buttons in building order, the floor you are looking at lit, gaps drawn as dead sockets. Click a floor to lift the one above it.

Up next

The now label carries what to do next; #48 tracks the visitor experience work. Issue #1 remains the overall spec. The visitor-experience and sponsored-floors branches add elevator arrival, original-prompt reveal, progressive image loading, contextual suggestions, and capped public creation. Sponsorship stays disabled until dedicated provider credentials are configured.

Known gaps, in order of how much they cost:

• At 100% zoom the tower renders generated floors at 60.9%, and nearest-neighbour resampling breaks the art up. #23 has the measurements and three ways out.
• Floors 13, 14 and 15 were drawn before the projection angle was specified and meet their neighbours at the wrong angle. Measurable, not repairable short of regenerating them.
• The light fringe around each tile's outer silhouette. Same root cause as the veins; #42 would remove the need for the fix rather than make it.

Focus

Visitor experience (#48). House cleaning (#35) follows this work.