Drag the mouse to pour heat and press F to put the fire out and light it again.
Each pixel is a heat: every frame it takes the heat of the pixel below, a little to the side, and loses a little. It runs on the graphics card between two createSpriteTextures that take turns, and anything written into them in white (the word) is a source of heat.
The colour ramp is cut into the original's 37 steps.