1. Where is the bookmarking feature? The star next to the score doesn't seem to do anything. If it's an icon to indicate score, it would be clearer to use a different icon.
2. For consistency, I'd use text headings at the top left of the time and score boxes, or at the very least put the icons on the left.
3. The 'View Solution' animation playback is confusingly fast. I'd add a step-by-step playback with forward/backward buttons as the default mode. You could still offer a checkbox to enable auto-playback, and a slider to adjust playback speed.
4. Since this seems to be based on the same toolkit Lichess uses, using the same color behavior for moves would be helpful.
5. Please offer a checkbox to enable showing possible moves when pieces are clicked like Lichess does.