This is a Vim trainer that grades how you edited, not just whether the buffer ended up right.

• It runs real Vim. The actual vim keymap, not a simulation of one. Every reference solution is replayed through it when the page loads — that is what the green badge in the header is counting.
• Every drill has a solution space, not an answer. It knows the idiomatic route, the ones that merely work, and the tempting wrong one — and it names which you took.
• Four dimensions. Correct, path, economy, and repeatable — that last one replays your keystrokes, presses ., and checks whether anything useful happened.
• It never runs out. Beyond the authored lessons, drills are generated for every technique and verified before you see them. practise anyway in the rail starts that at any time.
• Stuck is fine. Help has three rungs and the last one is the answer. It costs you nothing on the drill — only the review queue declines to credit a technique you read rather than recalled.