The Appearance page in File > Preferences... controls how LanSend looks. You can follow your Windows light or dark setting, or lock the program to one of them, and choose which theme is used for each.

The same choices are on the View > Appearance menu, so you can switch the look without opening Preferences.
Always light keeps the light theme regardless of the Windows setting.
Light theme is the theme used in light mode.
Toolbar and menu icons are vector graphics, so they stay sharp on high-resolution screens and match the active theme.
