Matrix Rain

What it does

Columns of green characters fall down a dark screen, each one led by a brighter character and fading out behind it. Press Start, or Go Fullscreen to fill the screen. Until you do, it is a still picture.

Speed and Density each have three steps. Calm is genuinely calm — about a quarter as many columns — and Slow halves the pace. Both can be changed while it runs.

Why the characters do not flicker

The familiar version of this effect swaps every character at random many times a second. Up close that is a shimmer; across a whole screen it is a flicker, and flickering screens are something this site does not show. Here each character keeps its shape for one to three seconds before it changes, and no two change at the same moment, so the rain moves without twitching.

Is it real code?

No. The characters are digits, capital letters and a few symbols, chosen at random. Nothing is being decoded, calculated or hacked, and nothing on the screen says anything about your computer. It is a pattern to look at — which is the honest answer to anyone who asks what you are running.

Using it

• For a spare monitor, go full screen and pick Slow and Calm; it reads as background rather than as something demanding attention.
• In a dark room, the dark background keeps the light low. For no light at all, the Black Screen is simpler.
• To leave it running, switch on Keep screen awake. It is off by default, held only while the rain runs, and the status line says whether your browser agreed.

For a screen with nothing on it at all while you work, there is Focus Mode.