Now with sparks

I added in a small chance for a cell to become white, with lower cells getting a greater chance. Tuned it a bit, to make it look like sparks in the fire.

First release

How to install on the Matrix Portal:

• Double click the reset button to enter boot mode. You'll see it when you get a USB drive named MATRIXBOOT.
• Drag and drop the FIRE.UF2 file onto the drive and sit back.