Research

The interface

The first phone sessions turned up the same problem in different forms: people couldn't find how to pick up colour, the tools were crowded into two wrapping rows, and the canvas was squeezed between them. This report asks what the best painting apps and mobile ergonomics research say, and turns the answer into a layout.

Findings

1. Most people hold the phone in one hand and work with their thumb. Steven Hoober watched over 1,300 people using phones: 49% held them one-handed and 75% touched with a thumb. The bottom third of the screen is the natural zone. In the top third, tap accuracy falls sharply and each tap takes longer. → Everything used while painting (tubes, tool, brush size) lives at the bottom. Rare things live behind a menu at the top.

2. Targets need at least 44 × 44 pt, with room between them. Apple's Human Interface Guidelines set 44 pt as the minimum. Smaller targets raise tap errors by 25% or more. → Tubes and tool buttons are at least 44 pt. Today's 26 pt tube swatches are too small.

3. Painters already know Procreate's gestures, so borrowing them costs nothing. In Procreate Pocket (the iPhone version): - two-finger tap undoes, and two-finger hold undoes rapidly - pinch zooms, and pinch-and-twist rotates - double-tap opens a six-button radial QuickMenu - touch and hold samples colour

Procreate calls two-finger undo "one of its most instinctive and essential gestures". → Two-finger tap undoes (this needs stroke history, built next). Pinch and twist moves the canvas. Touch and hold on the canvas picks up paint from the painting onto the brush, the physical version of the eyedropper.

4. The canvas comes first, and the interface gets out of the way. ArtRage Vitae is praised because it "maximises your creative space without hiding critical functions such as tool and colour selection, and as you paint it gets out of the way". Infinite Painter keeps one floating toolbar for brushes, colour, size and opacity, and puts everything else in a thin fixed bar. → The board fills the screen. Controls float over the bottom edge and fade back while a stroke is in progress.

5. The palette is a place, not a picker. Rebelle and ArtRage both give you a mixing palette where you paint, blend and pick up colour, because that's how physical painting works. That's also this project's first design position. → Tubes stay the main way to load colour. A slide-up mixing palette, where you mix with the knife and pick up the result, comes next.

6. Reference images are standard, and tracing is how many painters start. Procreate has a floating Reference Companion window, and an imported photo can sit over the canvas at low opacity for tracing. The owner works this way on real canvases: "I use an overlay paper to outline an image, and after getting the basic shape I do my work." → A Trace control: pick a photo, and it lies over the canvas like tracing paper, with an opacity slider. It zooms with the canvas, hides with a tap, and is never painted into.

7. The tool set should be what painters actually use. From Brushes and phone feedback, the brush (flat, filbert, round) and finger are daily tools. The knife is a real impasto tool but needs rework. The squeegee is one painter's niche. The rag, which wipes paint off to pull out lights, is a core oil technique that's missing. → Main tools: Brush (with its shape), Knife, Finger, Rag. The squeegee moves into Tests.

The layout

┌──────────────────────────────┐
│ ⋯  Fit               Trace   │  floating over the board: menu, Fit (when zoomed), trace
│                              │
│          the board           │  edge to edge, shaped to the screen above the dock;
│   (fills the screen, white   │  pinch to zoom
│    gesso to start)           │
│ ▮                            │  left edge: brush size, with a ring showing the true width
│ ▮                            │
├──────────────────────────────┤
│ [Flat▾] ┌──────────────────┐ │  the dock is the painter's shelf: the tool, and the
│ [Scrape]│ ● ● ● ● ● ●      │ │  palette itself: a blob of each colour, open glass below
│         │   (mixing glass) │ │  tap paint = load it; drag = mix with a palette knife
└─────────┴──────────────────┘─┘

One way to get paint: from the palette. The owner found tubes plus a separate palette confusing ("the bottom bar and the palette... not intuitive"). Two ways to load, a tube that behaved differently when the palette was open, and a hidden hold-to-mix gesture made three rules where a painter expects one. Now the palette is the dock, and it has two gestures:
Tap paint to dip the tool in it. It loads exactly what's under the finger, a pure blob or a mix. A different colour goes onto a clean tool; the same colour tops it up.
Drag to mix, whatever tool is in hand, as a painter mixes with a palette knife. The knife carries its lump and leaves it where it lifts, so dragging from a blob to a spot brings that colour there, and stirring folds it in.

The tubes never run dry: a blob that's mostly used gets a fresh squeeze. Scrape clears the glass and lays out fresh blobs. - Tool button: shows the current tool and shape, with the per-bristle load strip under it. Tap it for a sheet with Flat, Filbert, Round, Knife, Finger, Rag and Clean it. - Menu (⋯): light (Tilt, Lamp, Sway), touch feel, ground, Dry, New canvas, Paint a sample study, and the A/B switches.

Built

Layout: the board fills the screen above the dock, starting on white gesso. The top bar floats over it (menu, Fit when zoomed, Trace), and a size slider sits on the left edge. The top bar and slider fade while you paint.
The palette dock (finding 5 and the owner's feedback above): the tool button and Scrape on the left, the palette on the right. Tap paint to load it, drag to mix. It shares the paint engine (it's rows of the same grid below the board), so paint on it behaves exactly as paint on the canvas, and a stroke never crosses between the two.
Tool sheet: Flat, Filbert, Round, Knife, Finger, Rag, and Clean it. The squeegee is in the menu.
Trace: a photo over the board like tracing paper. See the test below.

Kinari: a Japanese studio, 2026-09-26

The owner asked for a better UI with Japanese inspiration. The references are practices, not motifs: no fake brushstroke kanji, no cherry blossom.

Nihonga painters mix on white porcelain dishes (e-zara), set out on a plain tray. → The palette is a white porcelain dish with a rounded rim, lying on a kinari (unbleached) tray. A mix is judged against the same white as the gesso it will go onto.
Ma: empty space as a material. → The chrome recedes to paper-coloured pills with hairline edges, and the canvas has nothing else on it. Controls fade while you paint.
Sumi ink and a seal. Text and icons are sumi ink. The one strong accent is shu, seal red: it marks the chosen tool (a seal dot), edges each hint slip, and is the lamp in the light pad. Selected segments are ink with paper text.
The ensō, the single brushed circle of Zen practice, is the menu button.
A brush roll (fude-maki), bamboo slats holding brushes side by side. → The tool sheet lays its tools out as slats, each an ink line drawing of the real tool.
One family typeface. Hanken Grotesk, as in Neshi, Nijimi and Furlong, with letter-spaced small caps for labels and the IMPASTO mark at the top of the menu.

The brush well and the colour fan (2026-09-26, the owner's design)

The porcelain dish was "not big enough, not useful", and the size slider "not easy to use". The owner designed the replacement: one radial control for the brush, bottom right in thumb reach. - The centre is the colour on the brush, the pigment mix rendered by the same model as the paint. - The outline shows how much paint is on the brush, as an arc. (Removed 2026-09-28: every stroke starts full, so there's nothing to gauge; see Refilling.) - Tap to pick up more of the current colour; on a clean brush it reloads the last mix. (Superseded 2026-09-28: every stroke now starts freshly loaded and the tap opens the colour rings; see Refilling.) - Hold, and the colour fan literally fans out: one leaf per pigment, pale near the centre and full at the tip, each with a line and quarter ticks. Tap near a leaf's tip for a lot of that pigment, near the centre for a little (10% to a full dose). Tap more leaves to mix; the centre updates as the mix forms. Tap the centre to close. - Size fits the same object: drag the well up for a bigger brush and down for a smaller one (about a doubling per 90 pt). An inner ring on the well is drawn at the brush's true width, and a ring in the middle of the screen previews it while you drag. - The brush keeps its size on screen, so zooming in (now to 10×) makes it finer on the canvas, fine enough to paint an eye. A barely-touching fingertip paints at 0.3× of the brush. - Occlusion: the trailing brush didn't work for the owner. The default is now a nib: paint lands 36 pt above the fingertip, marked by a small ring, like the tip of a pen. Trailing and painting right under the finger stay in the menu (Finger).

Quarter radials in both corners (2026-09-26, the owner's design)

The owner's reference is a collapsible radial menu from their own earlier work (Figma): a colour centre, a ring of tools, and an outer ring of swappable content, collapsing to one button. "We can't use it as is: we have a small surface." A phone corner holds a quarter of it, so each well opens a quarter radial with a few levels, and each ring gets the corner's full 90°. Items get wider the farther out a ring is, so the ring with the most items sits outside. - Right, the paint (one tap): inner ring = + (more of this colour) and the last two mixes; outer ring = the six pigments, far out for a lot and close in for a little, each leaf with its line and name. It stays open while you mix; the centre shows the mix. - Left, the tools (one tap): inner = Clean, Dry, Trace; middle = the six tools; outer = the swappable sets below. Picking a tool closes it; settings leave it open. - Swappable outer rings (the reference's "swappable menus"): drag along an outer ring and the next set rotates in, sliding under the ring's ends; or tap the tab above it, a dot per set (it showed the set's name until version 87). Left: Studio (Ground, Fit, Squeegee), Light (Sway, Tilt, Lamp), Finger (Nib, Trails, Under), Surface (Gloss, Shadows, Sharp). Right: Pigments, and Mixes (the last six). This is how a small corner holds more without growing: add a page, not a ring. - Both wells sit 18 pt from the bottom and side, concentric with the screen's rounded corner. While a quarter is open, the other well steps aside. - The rings start from the well's outer edge: each runs past its 90° until it meets the lines that touch the well at its side and bottom, and ends there in a straight cut, so the quarter sits square in the corner. Items sit an even 6 pt from every edge of their ring and 6 pt apart, and their corners nest inside the ring's (the owner's markup, 2026-09-26). - Visual quality: the rings are raised paper with a wide soft shadow and a tight contact shadow, a lit top edge and paper grain. Pigment leaves have body (grain and a bevel), tool tiles an upright icon and name, and the rings fan open one after another. The selected tool gets an ink outline and a seal-red dot.

Stored colours, straight rings, hold to open (2026-09-26, the owner's design)

The owner's next round (full sequence and screenshots in Design history, version 8): - The inner colour ring stores colours. Four slots and Clear. Tap one to select it; its colour goes on a clean brush. Each slot keeps its own recipe, so paint the brush picks up from the canvas never dirties it. - The outer ring adds one part per tap. Painters count mixes in parts ("two yellow to one blue"), and taps count the same way. Without a distance scale the ring is thin. - An empty colour opens a colour range: twelve hues mixed from the six pigments (so they stay paint-true), pale near the middle and deep at the edge. - Tap a well for the everyday thing; hold to open it. Right: pick up more of the selected colour. Left: back to the previous tool. A hold opens the rings with the finger down; slide onto an item and lift (a marking menu), or lift on the well to leave them open. - Tools show icons only, with the name as a tooltip above the finger while pressing. Every item acts on lift, so sliding off cancels. - Each ring is an L concentric with the screen's rounded corner: an arc, then straight on to the lines that touch the well. Colours and tools share one outline and one selected style.

Trace, tested

A still life (bottle, pear, a bowl of lemons) was laid over the board and outlined with a small round brush in ivory black, then the photo was hidden. What it showed:

It works for its purpose. The outline stays exactly registered with the photo, including when pinched in to 3× on the pear's stem, and the drawing left behind is clean and usable.
The photo was cropped. Covering a tall phone board with a 3:4 photo cut the bowl in half. → It now fits the whole photo by default, with Fill to cover the board.
The photo washed out the lines being drawn. It sat on top of the paint at half opacity. → It's now drawn with multiply, so it tints the white ground like a transfer and dark lines over it stay dark.
Its bar collided with the hint and the Fit chip. → Hints moved to just above the dock, and Fit moved into the top bar.
Long lines run the brush dry, as they would on real canvas. Tap the paint again between shapes.

A possible next step: an "edges" mode that shows only the photo's outlines, like a transfer drawing, for people who want the shapes without the photo's colours.

Next: undo (two-finger tap) and touch-and-hold pickup from the canvas. Both need stroke history.

Sources

Telling the brushes apart

The owner saw two brushes with the same icon (Flat and Bright; Round, Rigger and Dagger were close too). Two other styles were tried for a version, switchable in Studio: solid head silhouettes, and the mark each brush leaves. Neither was better, so both were removed (version 89), and the one set of icons was redrawn instead: shorter handles give the heads more room, Flat is tall with bristle lines, Bright short and wide with none, Filbert has a rounded end, Round is a plump point, Rigger a long hairline and Dagger a curved sweep.

What other painting apps do, as far as their brush pickers are known (not re-checked for this note): Procreate, Adobe Fresco, Infinite Painter and Rebelle list each brush by name with a sample stroke drawn by the painting engine; ArtRage shows a picture of the tool itself, with sample strokes in its presets. None of them relies on an icon alone to separate variants of one tool: an icon tells the families apart (brush, knife, eraser), and the name and the stroke tell the variants apart. In Enogu the name already shows as the finger slides across the brushes; a sample stroke painted by the engine is the step after that.