19 August 2026
Watch an old hand-drawn cartoon and hold your eye on a single still object. A table, a fence post, a hat on a hook. It will not sit still. The outline creeps and shivers a fraction of a pixel in every direction, several times a second.
That is line boil, and it is not a stylistic choice anybody made. It is a consequence. Every frame was drawn by a person, and no two drawings of the same fence post are identical. Play them in sequence and the difference between them reads as movement.
Vector art has the opposite problem. A shape drawn once and held is mathematically perfect and completely dead. Your eye notices the stillness even when you cannot say what is wrong. Boil puts the hand back in.
Our games use it on the objects you cut, the borders around every section of this site, and the type you are reading. The frame around this article is drawn, not stroked, and it is redrawn a few times a second from a different noise seed.
The naive approach is to animate a noise filter continuously, which forces the browser to rasterise turbulence on every frame. On a phone that is brutal. The cheaper trick is to define two or three fixed displacement maps and swap between them on a step timer. The eye cannot tell the difference and the work is done once.
We built a free Mac app called Boiler that applies the same effect to any video. Drop a clip in, get one back.