For better development experience, the platform set up a postcss process for auto-detection and prepending the correct selector (i.e. either #light or #dark). To activate this feature, you only need to define your styles by less file and rename it to either [filename].light.less or [filename].dark.less; We also accept light.less or dark.less for short. The process will detect its extension and prepend the prefix to all styling within the file.