I was definitely matching Mahjong tiles by color
I didn’t notice it at first, but I was barely looking at the actual symbols. I’d scan the board, spot two tiles with similar colors and assume I had a match.
That worked until I got a layout full of tiles using almost the same color palette. I kept passing over obvious matches and then finding them a few seconds later, right in the area I’d already checked.
Since then I’ve been looking at the shapes first and the colors second. It sounds like a tiny difference, but the board feels much easier to read when I’m not letting the color scheme do all the thinking for me.