That "racing to the end" is actually good, it means you've hit one at the right point in time. I know it lacks somewhat in good feedback, and I have some ideas on how to fix that in mind, but they didn't make it into the Jam release. (As did the suggestion by my testers to provide at least a rudimentary way to define different keys which would be by providing a configuration file to be read. In a first iteration it should just read that file if one was prepared manually and eventually with some sort of setup screen. One of the many things to address when I get to it...)
And yes, blocks are only vulnerable while they sit still on a tile, not while they're moving...