Adding to what you both said. I run pixel checks against live websites in a real browser, and I stopped doing full-page screenshots early on: scrollbars, lazy-loaded images and font timing shift pixels between runs like clockwork.

What works for me is diffing small stable regions, one component or one flow at a time, with a small per-pixel tolerance. I also keep a DOM-level assertion in front of the visual check, so when something fails I already know what changed structurally before I compare two images.

For the game port it's genuinely harder, the renderer decides the pixels, not the test. But the region idea transfers: lock the viewport and only diff what's stable.