How this notebook is made

A pied wagtail, drawn on a single canvas from a handful of ellipses and lines. It only ever stands on real lines on the page — section rules, the edges of cards, the underline beneath a heading — and it re-reads where those lines are as the page moves.

From there it does what the bird does. It pumps its tail in bursts. It watches your cursor, and hops along its line towards it — but stops short. Lunge at it and it flies. Scroll and it follows you, landing on whatever line is nearest. Leave it alone and it potters about, pecks and turns round. Click right beside it and it calls.

It has a home, too: the cage hanging in the top corner of the page. When there is nowhere left to stand it flies in there rather than off the screen, and lets itself out when a line comes back into view. Click the cage to call it home; click again to let it out.

Under the cage is a packet of seeds. Click it and four to six seeds land on a line near the bird. It goes straight to them and eats them one by one, bowing down to peck, and is too busy to mind your cursor until they are gone.

Then it sings. Its head goes up, its beak opens on every note and notes drift off into the margin — out loud too, if the song switch under the packet is on. The song is different every time and is made in the browser as it plays; there is no sound file.

The card beside this is reading the bird as it goes. Move your cursor towards it and watch the numbers change.