Paste PGN — a Lichess study (Study → Share & export → Study PGN), a ChessBase export, or any game with variations. Each variation becomes a line to drill.
Tap a chapter's side to switch which color you play. Untick chapters you don't want to drill.
Settings
Back up / move to another device
Sync across devices
Keeps studies and progress in step between your Mac and phone using a private GitHub gist.