Thanks for the great feedback Ishi! I loved Lemmings too but funnily enough this never started out as a Lemmings-alike. It actually started out as a platformer believe it or not, but naturally evolved into a puzzle game the more I worked on it. I'm sure somewhere along the line I was subconsciously inspired by Lemmings though given the similarities!
It struck me as a little odd in the video that the followers walked in the other direction after changing surface. For example if they're walking left, and fall from the ceiling down to the floor, they then walk right.
I struggled with this for ages at the beginning! I totally agree, it looks odd. The thing is, they aren't changing direction (in terms of the in-game logic at least!). For example, when a follower walking rightward "falls up" and starts walking on the ceiling, its direction is still "dir=RIGHT". It's only moving to the left from the player's perspective. Even so, I still struggled with this for a long time but then I realised how many of the puzzle elements come from the combination of direction and gravity so I stuck with it.