Hi! I played a few runs (I might not have gotten as far as I'd like), but my memory skills are very grateful :)
I haven't seen such an engaging way to improve my memory in a long time. The game looks very cute and can be quite addictive.
I didn't notice any bugs, but I have one suggestion for a small adjustment: when you're typing a letter combination and reach the point of entering a single letter, but decide to delete one or more letters, first one letter is deleted, then another letter from a pair, and then two letters at a time. In other words, letters are deleted out of pairs (I hope I explained it clearly; my English isn't very good.)
Good luck with the development :)