If you get something wrong, and what you type is longer than the expected answer, you end up failing the next couple of questions too.
muscle memory - if you type eg "uptime" when the answer should be "free", it fails on the first character, but you're still typing, by which time it's on to the next question. which you then fail, because the answer to the next question isn't "ptime"
Yeah, this is a problem. Also, having some nice visual feedback when I get one right or wrong would be great.
That said, this is an awesome service and I'm going to pay for the premium account just to support the effort. I'm in the process of switching from a tricked-out gedit along with nano to just using vim, so this is a wonderful resource. I'd highly recommend it to anyone trying to learn vim. In the course of just 10 minutes, I've already learned another 10 commands. Assuming I practice them another day or two, they'll become permanently part of my vim repertoire.
EDIT: To clarify what exactly I'm using this service to do: I'm using it to eliminate the constant need to refer to a vim reference card. The muscle memory will come only from using these commands in vim, but being able to eliminate the need to constantly refer to a vim reference for new commands is a huge plus. I've already learned 10+ new commands that I no longer have to look up. PS - paid for the premium.
muscle memory - if you type eg "uptime" when the answer should be "free", it fails on the first character, but you're still typing, by which time it's on to the next question. which you then fail, because the answer to the next question isn't "ptime"