Aquarium countdown timer

At a glance

Why there is a fish tank on a timer

The origin story of the aquarium skin, from the people who drew it.

The aquarium began as an answer to the most common question in a room with a small child in it: how long? A five-minute warning means very little at that age — “five” is an abstraction, and a number counting down is just another number. A tank of water is not. Show a kid a tank draining toward the sand and they can see the answer from across the room, without reading a single digit.

That is also why the tank is drawn as a physical place rather than a progress bar. The water line wobbles like a surface, not a spreadsheet. Two weeds sway on the sand and keep swaying after the water has dropped past them — now in air, slower and sadder. Bubbles rise from the floor and pop at the surface line, wherever it currently is. The fish cruise on lazy sine-wave paths, and as the pool shrinks, their wide laps tighten into small circles so they always stay inside the water that is left. Nothing is punished when time runs out; the fish simply settle into the shallows and wait.

Drawing the fish came first, and the details that make them feel alive are small: a body that is a gradient from back to belly, a tail that wags faster while the timer is actually running than while paused, an eye with a single white glint. The species followed — a clownfish in orange and a teal companion, a rounder goldfish, a slim neon tetra — and “random mix” for people who just want a busy tank.

The four waters came from requests: ocean blue for the classic look, deep sea for a darker room, lake green for a nature table. Sakura pink was the last, added because a cherry-blossom tank photographed beautifully on a classroom wall — and because a pink aquarium is the kind of wrong that turns out to be entirely right.

How the scene moves

• Idle. The tank sits nearly full — the water line starts 14% of the way down the stage — with fish cruising and bubbles occasionally rising.
• Running. The surface wobbles and sinks with the countdown, from that high line down to 78% of the stage height. Fish swim a little faster, tails wagging, and the weeds drift between “under water” and “not”.
• The last stretch. The pool is shallow; the fish tighten their circuits and settle into what is left. Fewer bubbles, quieter scene — the room leans in.
• Zero. The chime plays three fat water drops and a soft two-note surf chord. The readout flips to +mm:ss overtime so late finishes stay honest, and the tank holds still until you reset.

Make the tank yours

The sliders button in the bottom control row opens Scene settings. Every option below is stored in your browser and survives reloads; nothing is sent anywhere.

Two shared panels live in the same place for every skin. Sound picks the finish chime (or “match the skin”), sets the volume, and adds an optional tick for each of the last ten seconds. Display moves the countdown readout — bottom, top, centre, bottom-left or bottom-right — and recolours it: follow theme, warm white, white, gold, ice blue or coral.

Copy-paste links

Tank options travel in the link itself, so a configured aquarium opens the same way for whoever you send it to:

The sound it makes

When the tank empties you hear three plump water drops — a downward, then upward bend — followed by a gentle two-note surf chord. Like everything in timer.cool, the sound is synthesized by the browser at the moment it plays, so there is no audio file to fail loading and nothing to download. You can keep it, swap in a bell, digital beep, wood block or alarm from the Sound panel, or mute entirely with M.

On a projector or TV

The aquarium is at its best on the room’s biggest screen. Open the timer, press F, and every control disappears — the tank and the readout are the only things on screen. While a timer runs, the page holds a wake lock so the display does not dim mid-story.

The keyboard map: Space start/pause, F fullscreen, R reset, M mute, +/− give or take a minute while running, L repeat. Two honest limits: on an iPhone the ringer switch silences web audio, and aggressive battery-saver modes can override the wake lock on some devices.

Who the aquarium is for

Questions