Show HN: Koi.rest – watch some fish and regain your balance
Koi.rest is a minimalist web app that fills your browser tab with a looping aquarium of koi fish, letting you step away from the terminal for a few seconds of calm. The project is built with vanilla JavaScript and CSS animations, showing that you don’t need a heavy framework to create a pleasant, responsive visual experience. Its source code is openly hosted on GitHub, so you can dive into the rendering loop, the subtle easing functions, and the way the canvas is kept lightweight even on low‑end devices.
The appeal for developers goes beyond the soothing visuals. By watching the fish glide across the screen, you get a natural reminder to pause, stretch, and reset your posture—something many of us forget when glued to a monitor. The app even includes a tiny timer that nudges you to take a break after a set interval, turning a simple screensaver into a productivity aid that respects the Pomodoro principle without forcing you to install extra extensions.
From a technical standpoint, Koi.rest demonstrates a clean separation of concerns: the fish animation logic lives in a dedicated module, while the UI controls are handled by a lightweight state manager. The codebase makes good use of requestAnimationFrame for smooth frame rates, and the fish trajectories are generated using a combination of Perlin noise and simple physics, offering a nice example of procedural animation that you can adapt for games or data visualisations.
If you’re looking for a quick project to tinker with, fork the repo and experiment with new fish species, different water effects, or even interactive elements that respond to mouse movement. Adding a WebSocket hook could let you broadcast the aquarium state across multiple browsers, turning a personal break tool into a shared, collaborative experience. Either way, Koi.rest is a reminder that a few lines of code can create a calming oasis right on your development workstation.
Source: Show HN: Koi.rest – watch some fish and regain your balance