Show HN: Zero – a mathematical puzzle game

I like the colors; I found after a few seconds I was just looking at the colors and not the numbers. The 6 and 4 are a bit too similar in color, though.

slightly addictive, but I found myself thinking the sum is the amount needed to get to 0, rather than the amount currently on. e.g. when it says 6, i look to get 6 rather than 4