However, I've locked myself a few times so it was impossible to go on without using 'up' (or whatever): x x x x x x x x o o o o o o o o where at no point t

However, I've locked myself a few times so it was impossible to go on without using 'up' (or whatever): x x x x x x x x o o o o o o o o where at no point the same numbers next to each other allow collapsing. Maybe it's the problem not growing from the corner.. hm.