I'm running it on Chrome with macOS 26.6.2 (M4 Mac Mini), and I haven't tried the downloadable build yet. For the performance, I noticed the lag happens a bit whenever I'm facing a large field of flowers, while facing the sand feels much smoother.
For the UI, the overall quality of the game is already pushed to a really high standard, so the UI just felt a bit stiff in comparison. Not sure if it's intentional, but clicking buttons and opening/closing menus lack a bit of juice and snappy feedback. Also, in-game HUD elements like the Boost bar in the bottom-left feel a little rough and don't quite match the polish of the rest of the game—making the HUD layout a bit cleaner and more cohesive would really elevate it. Hope this helps!