Sign in, or create an account
An account scores 5 mashups a day on the daily leaderboard — the same five for every account, paid or not, because the board has to be the same game for everyone on it. Drawing without an account still works — those mashups are saved and shareable, they just do not compete.
There is no separate sign-up and nothing to remember: an address that has never been here gets its account on the first link, and every link after that signs the same account back in.