A smoky, cloud-style generative screensaver

Difference clouds is the one to try. It sits in the night pack of Screensavers by Zaweba and combines two drifting noise layers so that glowing veins of light ripple through the dark, rather like smoke lit from within. You choose the colours, the speed and the amount of detail.

If you've used an image editor's difference clouds filter, the name will ring a bell. The idea is similar: layers of soft noise combined so the places where they meet glow. Here, though, the layers move, so the veins shift, split and join continuously.

How it's drawn

The pattern is worked out on a small grid and then stretched to fill the screen. That's why it looks soft and smoky rather than sharp, and it also keeps the work for the computer light. The two noise layers drift independently, so the glowing veins never settle into a repeating loop.

Colours, speed and detail

There are five colour choices: moonlit greys, violet night, embers, deep teal, or changing slowly. Moonlit greys is the subtlest, like mist under a moon. Violet night is cool and dreamy. Embers glows orange and red, like the inside of a fire. Deep teal is calm and watery. Changing slowly moves between colours over time, so the screen never looks quite the same twice.

Speed and detail each run from 1 to 10. Low speed makes the veins drift lazily, high speed makes them churn. Detail sets how fine the structure is: low detail gives broad, soft clouds, high detail gives intricate threads of light.

A low speed with medium detail in moonlit greys is a good place to start for a calm screen. Embers at a higher speed is more dramatic.

Making it the PC's screensaver

Open Screensavers by Zaweba and select Difference clouds. Adjust the colours, speed and detail while the live preview follows them. Press Preview full screen to see it at size, and move the mouse, click or press a key to come back. Then press Use this screensaver. It's built into your Windows profile with no administrator rights, and Windows' Screen Saver Settings opens so you can choose it and set the wait time.

The screensaver reads its settings each time it starts, so trying embers next week costs nothing but a click.

A dim screen for dim rooms

Difference clouds is mostly dark, which is what the night pack is about: a dim screen with a few bright moving things. It's a good choice for a bedroom monitor or an evening office. On several monitors, run one on each, stretch one across them all, or keep it on the main monitor and blank the rest.

Its natural companions are Growing foliage and Paisley layers, the other slow generative pieces in the pack. Tick all three and use Install several for one screensaver that picks among them at random.

Gentle on the hardware

Because the pattern is calculated on a small grid and scaled up, it's light work for the computer. Laptops also have a frame cap of 30 or 60 frames a second and a battery saver in Install and options, which blanks the screen on battery below a chosen charge, 25 per cent by default.