Controls nicely, but the one bad monster's home-in-on-you movement is kind of unmistakable (and fairly difficult to counter, honestly). If you do have the exits only open once the bad monster's destroyed, I might actually suggest slowing them down a bit so you actually can challenge them.
Love how the music all shares a common melody, showing very clearly that it's original for the game. I could feel the effort that went into it.
Also, and this is just me: the simple gameplay here doesn't jive well with my Undertale-derived understanding of friendly monsters :)