In the game
Open Settings and choose Delete account. It is immediate.
Without the game
Email support@leaktd.com with the subject "Delete my account", your player ID and your deletion code (Settings shows both next to Delete account: press Show, then Copy). We delete the account within 30 days and reply to confirm. Accounts are not linked to an email or phone number, so we need the player ID to find yours and the deletion code to know the request is yours: other players can see a player ID, and a display name is not enough either. For a child under 13, a parent can send just the player ID.
What is deleted
Your account and the install ID it signs in with; your display name (it becomes free for someone else); your profile and progress — your experience and level, games played and won, recent results, and the portrait and banner colour you picked; your place on the ladder; your friends list (you disappear from your friends' lists too); and the invites to private games you sent or received.
What is kept
Records of past matches may still contain the deleted account's ID, so other players' results stay correct, and small anti-abuse counters (how often an address or an account signed in or used an online feature, such as making, joining or finding a game) keep the ID or IP address until they are cleared within 30 days. Match statistics (how matches went and how connections held up) use a scrambled player code instead of the account ID and are deleted 90 days after each match (copies of the moves kept for training computer opponents, which hold no code or name: 2 years). The ID is no longer linked to any phone or person. Server logs that may hold it are deleted within 14 days, and backups within 30 days. We keep a note of the request (the account ID, the date and what was done) for one year.