This is really well designed. It's so much work to prepare your path to the exit, and then there are good optimisations on top of that. It's brilliant that the level was intentionally designed to work like this.
Edit: Ah, unfortunately there are lots of duplicate solutions for the top-right part.
Fun design, nice trick, took me many attempts. Found myself thinking things like "OK I've ruled out column A, let's try column B... now I've really ruled out column B, I'll go back to A... but now I've really really really ruled out A, so back to B again" - except this was happening with 8 columns