How it works
Like chess tactics, only your first submission counts. Solve it and you gain ELO while the problem loses some. Fail or surrender and it goes the other way. Expected score: E = 1 / (1 + 10^((Rp − Ru)/400)). Your K starts at 64, drops to 40 after 10 rated problems and settles at 32 after 30, so your rating finds your level quickly (it shows as provisional until then). The problem's K is 16. The next problem is picked close to your rating, varying topic and database. You can also search the bank and pick any problem from the bank; one you already attempted is practice and does not change any rating.
If a problem looks wrong or unclear, use “Report problem”: it is hidden for you and its rating effect is undone. Part of the bank is adapted from the gretelai/synthetic_text_to_sql dataset (Apache License 2.0), filtered and reviewed automatically.