Background

When Step 3 · Locate & Segment cut your objects out, it left a hole where each one used to sit. Step 4 · Background repaints those holes into one clean, complete backdrop — the art behind your sprites, rebuilt in your scene's own style. You work in two stages: generate whole-scene takes and put the best one in use, then refine any spot that came back wrong. You are done when the backdrop reads as a single seamless scene with no ghost of a removed sprite. Continue to Mask Sprites then flattens everything into the one background image every later step consumes.

Two stages, one live brush

The right rail is two stacked cards: ① FILL HOLES (indigo) and ② REFINE (amber). Both can be open at once, but exactly one is armed — the glowing header, ARMED · red brush or ARMED · amber brush, names the brush the canvas is using right now. Clicking anywhere inside a card arms its stage; the chevron on the header only collapses or expands the body.

The brush also follows what you are looking at. Paint while the holes are showing (Mask or Cutout view, or a peek) and you edit the hole-mask; start painting over a take and Stage ② arms itself, the brush becoming the amber Refine brush on the first stroke. You never have to click a header first — whatever the canvas shows decides which brush you get. The {NN}% button at the top right prints the current zoom and resets it to 100%; scroll to zoom and drag empty space to pan.

Stage ① — Fill the holes

On entry this stage is armed and the canvas opens in Mask view, the red hole-mask laid over your original scene. Generating a take lifts every sprite out and repaints what was behind it.

1. Scene row — the undeletable Background layer. Click it to edit its hole-mask; S solos it, the eye toggles visibility, and a double-click renames it.
2. Prompt for the Background fill — the instruction the AI fills with. It starts on a sensible default; edit it to steer the repaint, or hit reset to restore it.
3. Settings ▸ AI model — a disclosure holding the model picker. Each option prints its credit cost, and one is marked recommended: it repaints hard, cluttered areas far more reliably than the cheaper option, which is worth it whenever a budget fill leaves holes behind.
4. Generate take — spends credits and adds one take to the grid. It is disabled while a generation runs or when the Background has no holes to fill.
5. Pick a take — each tile shows a thumbnail, a T1 label, and a fill badge (✓ filled, or ✗ 2/5 unfilled when the AI left punches un-repainted). Clicking a tile installs it as the backdrop at once — selection is installation, with no separate apply. Click the active tile again to peek the holes underneath (◌ hidden — holes show) without changing anything.
6. + take — the dashed tile at the end of the grid rolls another take from the same prompt. Variety is the point: generate a few and keep the best.

To remove a take, hover it and click the red ×. That opens a confirm dialog and is permanent.

The canvas toolbar

A single chip toolbar sits above the canvas. In the Fill stage the right-hand group edits the hole-mask; every control here is free.

In the Fill stage, once a take is showing, three floating buttons appear at the top-left of the canvas: Back to mask returns you to editing the holes, Compare drops a wipe divider between the original scene and the filled backdrop (drag anywhere to move it), and Hold: original (C) flashes the original while you hold the button or the C key. In the Refine stage Back to mask drops away — only Compare and Hold: original (C) remain — and the right-hand toolbar group collapses to a single New region button.

Smart merge or Whole image

The switch under the takes grid decides how the take you installed becomes the background.

• Smart merge ★ (the default) keeps your original art pixel-crisp everywhere outside the holes, and snaps then feathers only the fills into place along matching pixels. It is the seamless choice when the take is good.
• Whole image makes the entire take the background. Every pixel is AI-redrawn, so it is uniformly seamless with no interior seams — the escape hatch when a merged spot bothers you.

Flipping the switch re-composites instantly and costs nothing; both forms are already computed. With a smart take in use, a verdict line reports each hole — Smart merge: 5 holes · 3 snapped · 1 wide-blend ⚠ · 1 unfilled ✗. If any hole drifted or came back empty, an amber advice chip appears suggesting you paint that spot in ② REFINE, re-roll a take, or flip to Whole image.

Stage ② — Refine a spot

The amber card stays locked (locked — pick a take first) until a take is in use. When a take is right except for one spot, fix that spot instead of re-rolling the whole scene. Each fix is a stacked touch-up with its own prompt, attempts, and coverage.

1. ＋ new region — start a fresh region, or just paint amber over the result; the first stroke arms the stage.
2. Generate this region — from the painted draft, this makes the touch-up's first attempt. It is disabled until you have painted something.
3. Touch-up section — each finished touch-up gets a row: S solo, thumbnail, {name} · 2 attempts (double-click to rename), the visibility eye, up/down arrows, delete, and a chevron. Opening one shows its amber region on the canvas.
4. Touch-up prompt — describe the change for this region; left empty it falls back to a default.
5. Regenerate this touch-up — adds a new attempt for this region, brush edits to the amber mask included.
6. Attempts — a thumbnail per attempt; click one to make it the shown result (#2 shown).
7. This fix covers — flip between Region ★ (only the clip changes, the default) and Whole image (this attempt's full frame replaces the whole backdrop). Whole image is unavailable for attempts made before the option existed until you regenerate once.

Touch-ups list in creation order, and the lower one wins where regions overlap — the up/down arrows reorder that. Only the amber area ever changes; everything else stays pixel-locked, and a failed attempt simply leaves the area as it was, so re-rolling is always safe.

Continue to Mask Sprites

Every artifact here — the Background, the take in use, and any touch-ups — is a layer in a stack local to this step. Continue to Mask Sprites flattens that stack into one background image and advances to Step 5 · Mask Sprites. You can leave and come back: your brush edits survive, and any object segmented later punches a fresh hole for you to fill.