Settings
Theme, fusion calculator behavior (animated reveal, auto fuse, show both orientations), custom sprite visibility, and card backgrounds. The same options are in the header settings dialog and on the calculator where relevant.
Appearance
Theme
Light, dark, or system.
Mode
Graphics looks richer. Performance is faster and lighter. Best if you use the site for data and browsing, not just casual fun.
Fusion calculator
Same as the switches on the fusion page.
Display
Color behind sprites in lists and previews.
Home, All Sprites, and New: show mostly the sprite until you hover.
Use the gear in the header anytime to open these settings.