Sure - so this level's a bit tricky. And trying to solve it with trial and error can become overwhelming.
In essence though, player B just needs to trigger the falling blocks in the correct order. So you can start by deducing that the large block closest to B's starting location cannot be touched first, because it would permanently block A's escape. Then you can consider the smaller block touching that block at the bottom right - you can touch it first without trapping A, but then B either has to go down to that lower area (where they'll be stuck), or touch the first block we looked at, which again would trap A. So you can rule out that block as the 1st touch too.
You can kind of proceed in this manner, deducing which blocks are touchable in what order to solve the puzzle.