This is not a big deal, but I figured I’d report that I noticed when doing the lesson for 止まる at level 5 it says:
… you can bet that it will use the kun’yomi reading. You didn’t learn that reading with this kanji, so here’s a mnemonic to help you:
However, that isn’t true because the 訓読み reading of 止 (aka と) was learned as a part of 止める at level 3. Incidentally, the level 3 lesson (correctly in that case) makes the same claim.
I imagine the order of the vocabulary changed at some point.