Hot Cocoa by the Window

What you can do here

Move the steam

Move your pointer or finger through the steam and it swirls after you, the way it does when you wave a hand over a cup. Keep still and it goes back to rising and curling on its own.

Melt the frost

Hold a finger or the mouse button down on the frost at the edges of the glass and it melts into a clear, wet patch. Drag to draw a line through it. The glass is cold, so it frosts over again in about a minute.

Watch the frost grow

New fronds of frost creep in from the edges of the pane about as slowly as real frost does. You won’t see them move, but look away for a few minutes and they’ve grown. They stop after eight or nine minutes.

Make it hotter

Cocoa sets how hot the cup is: just poured, it steams hard; warm, only a few thin wisps come up. Tap the cup, press Stir or press C and you hear the spoon against the mug, and a thicker run of steam comes up for a few seconds, the way stirring brings the hottest cocoa to the top.

Change the snow

Snowfall goes from a few flurries to a heavy fall. You see the flakes best against the dark shrubs and the stone wall; against the white lawn they all but vanish, as they would from a real window.

Put on some music

Music plays apart from the scene’s own sound, with its own volume, so you can have either, both or neither. It starts on this scene’s pick and repeats it; open the list to choose another, play them all in order, or shuffle the ones you tick. There are fifteen, all instrumental: twelve carols, from Jingle Bells to O Holy Night, and three pieces written for these scenes. Music only starts when you start it.

Use it as your wallpaper

Press F for fullscreen and M to turn the sound off and on; the volume and your sound choice carry over to every wallpaper. The sound keeps playing if you switch to another tab.

Live link

On a computer desktop

Some wallpaper apps can show a web page behind your desktop icons. Give one the live link above and the scene runs there on its own: no page around it, no ads and no sound.

On a TV or a spare screen

Open this page and press F, or use Fullscreen. While it’s in fullscreen we ask the browser to keep the screen from going to sleep.

On a phone or tablet

Save image downloads exactly what’s on the screen as a picture. Set it as your wallpaper from your photos; the phone will crop the sides.

A live wallpaper keeps a page running all day. Through the live link the scene draws at most 30 frames a second and stops while the screen is covered, but on a laptop it still costs some battery.

Why steam shows against dark things

What you see over a hot drink isn’t water vapor, which is invisible, but tiny droplets that form when the vapor meets the cooler air. They scatter the light from the window, so they show up pale against the shrubs and the cocoa and disappear against the white snow behind. A little higher up they evaporate again into the room’s drier air, which is why steam fades out instead of rising forever.

How fern frost grows

Frost on a window starts where the glass is coldest, at the edges by the frame, often from a scratch or a speck of dust. Ice crystals are six-sided, so branches split off at about 60 degrees, and each branch grows fastest at its tip, which gives the fronds their feathery look. The new frost here grows the same way, a branch at a time, out of the frost already in the picture.

About the sounds

Two recordings: the quiet of a room on a winter day, and a spoon against a mug. Steam and frost make no sound you could hear, so nothing plays for them.

If you’d rather just watch

• Snowy Window, a drawn winter window screensaver
• Snowfall Window, snow falling past a window seat