The daily challenge and the leaderboard
One challenge a day, and a weekly leaderboard that lists only the people who choose to be on it.
The daily challenge
One small circuit task, the same one for everybody, a fresh one every UTC day. It is on /learn, with the lesson it came from, the step's own title and what the check is looking for.
It is drawn from the lessons rather than written separately, because a task the simulator already knows how to judge is a task that cannot be wrong. Only steps with a real checkpoint are eligible: a step that asks you to tick a box is not a challenge.
Finishing it is worth 50 XP on top of the step itself.
How the day's task is picked
A hash of the date and nothing else. No account, no randomness and no server, so two people on two machines get the same task and the server agrees with both of them without being asked.
Tomorrow's is knowable today, which is fine. It is a warm-up, not a quiz.
By email
When you finish a lesson signed in, the lesson offers Get tomorrow's 2-minute challenge by email. Say yes and the day's challenge arrives once a day, from noon UTC, at your account's address, with a button that opens it on the right step. Never more than one a day.
It needs a confirmed address, so the offer only appears once you have followed the confirmation link sent when you signed up (an account made with Google or GitHub is confirmed already).
To stop it, use the unsubscribe link at the foot of any of them, your mail app's unsubscribe button (which takes you off every list at once), or the Email section of your account page, where it is the Daily challenge checkbox. Turning it off there leaves the newsletter lists as they were.
The weekly leaderboard
Also on /learn: experience earned since Monday.
It is opt in, and off for everybody who has not said yes, which is why the switch is the first thing on the card rather than a setting somewhere else. It shows a first name or a username and nothing else.
Signed out there is nothing to draw at all, because a board of one browser is not a board. The card says so in one line and offers an account.
The friends board
The same week, fed by the invite link: people who came in through your link, and whoever's link you came in through. If invites are not set up, the card simply does not draw it. See invites.
Weekly leagues
On /progress: join and you are put in a league of up to 30 people for the week, ranked by the XP each of you earns from Monday. A fresh table starts every Monday (UTC), and the top three earn the hidden Podium feat, paid the next time you visit.
In a league you appear as a nickname made up for you, two words and a number such as "Swift Capacitor 42". Never your name, your username or your email. You can ask for a new nickname or leave the league at any time.
Leagues are off for students in a class: their XP, streak, quests and badges are all still theirs, privately.
Not in the classroom
None of this is on the class pages. A class dashboard is a roster and a set of submissions, and a league table of XP is not what a teacher asked for.
The weekly goal
Separate from the leaderboard and not competitive: five lesson steps a week, out of the box, drawn as a ring. Reaching it the first time in a week is worth 60 XP. See XP and levels.