Anticode Open builder

Build a drawing app with brushes, colours and undo that feels good under a finger

A drawing app is judged in the first stroke: does the line follow your finger without lag, and does it look like ink or a jagged polyline? Anticode can build a paint app on the browser's canvas with brushes, colours, undo and saving as an image, working with touch, mouse and stylus. Here's what to ask for, including a version for children.

Updated · By the Anticode team

What makes a stroke feel right

The difference between a toy and a pleasant sketch app is mostly in how strokes are drawn:

  • Pointer events for everything. One input path for finger, mouse and pen, so behaviour is the same on a phone and a laptop.
  • Smoothing. Draw curves through the sampled points rather than straight segments between them, with a little stabilisation for shaky hands.
  • Pressure, where available. Many styluses report pressure to the browser; width and opacity can follow it. Mice and fingers usually report a constant, so the brush needs a sensible default.
  • No lag. Draw the current stroke immediately and do any heavier work after the pen lifts.
  • No accidental scrolling. The canvas must capture touch so a stroke doesn't scroll the page.

The tool set

Brushes
A pencil (thin, hard), a marker (wide, flat), a soft brush (feathered edges) and an eraser. Four good brushes beat twenty mediocre ones.
Colour
A curated palette of 12 to 16 colours plus a picker for anything else, and recent colours. An eyedropper that picks from the drawing is a small luxury.
Size
A slider with a live preview circle.
Fill
A bucket fill for closed shapes, with a tolerance so anti-aliased edges fill cleanly. Kids use this more than anything.
Layers
Optional. A background and two or three layers covers most hobby use; full layer stacks add complexity many people never need.
Undo and redo
At least 30 steps. Store strokes, or snapshots every few strokes, so undo is quick even on a phone.

A kids' drawing app

For children, change the priorities: huge buttons with drawn icons, no tiny sliders, a few fat brush sizes, bright colours, stamps (stars, hearts, animals drawn in code), a bucket fill and a big friendly undo. Hide destructive actions: "New picture" should ask in the page before clearing, since a lost drawing upsets a four-year-old more than any bug.

There's also a safety argument. An app built in Anticode's sandbox has no network, so there are no ads, no in-app purchases, no chat and nothing a child can wander off to. Their pictures stay on the tablet. Links elsewhere open only if you put them there.

Saving drawings

The natural output is an image file. Ask for Save as PNG (with a transparent background option), and test that the download works on the phone or tablet you'll use; on some tablets the image goes to the files app rather than the photo library. A gallery inside the app can keep recent drawings in the browser's storage, but that holds only a few megabytes, so keep it to small thumbnails or a handful of pictures and treat downloading as the real save.

Describing it to Anticode

"A drawing app for a tablet and a phone. Pointer events, smoothed strokes, pressure from a stylus where available. Brushes: pencil, marker, soft brush, eraser. A 16-colour palette, a colour picker and recent colours. Size slider with preview. Bucket fill with tolerance. Undo and redo, 50 steps. Save as PNG. A kids' mode toggle with big buttons, stamps and three brush sizes. Canvas fills the screen, tools in a slim bar that hides while drawing."

Anticode's model writes it with the browser's Canvas, so no outside libraries are needed. Test on the real device: draw quickly, draw slowly, use two fingers, rotate the screen mid-drawing.

Limits

  • No photos from the camera to trace over; the sandbox has no camera access. Opening an image file already on the device might work if you ask for it; test it.
  • No sharing to a gallery or social media from inside the app; download the image and share it yourself.
  • No AI to tidy, colour or generate art.
  • Not a professional painting tool. For print-resolution illustration with brushes from a library, a dedicated art app is the better fit.

For diagrams with boxes and arrows, the whiteboard app suits better. For art made by code rather than by hand, see the generative art app; and for a children's site around the app, websites for kids.

Questions people ask

Does the drawing app work with a stylus?

Most tablets report stylus input, including pressure, to the browser. Ask for pressure support and test it on your device.

Is it safe for young children?

It has no network, ads or purchases, and drawings stay on the device. Supervise as with any screen time.

Can I keep drawings between visits?

A small gallery can be kept in the browser. Download the PNG to keep a picture for good.