This immediately reminded me of "Man in Gap" by kevinresol, but wow, with what a twist (even literally)!
I liked how there's a guideline for where the walls meet on double-wall modes - it really helped as soon as I realized that's what it was... Also, the player level names made me giggle and I absolutely loved the groovy soundtrack.
No real downsides I can think of, if not for the fact that I couldn't get past Tumbler Mode, trying my hand at this on a track-pad. Must come back with a mouse someday soon, and see if that'll help me be quick and accurate enough.