Steel

Of course there's one more option which would be to go for the ceiling, but it'll take the longest as it requires footholds and handholds. They'll also need to be relatively deep.

Behind the left wall should be the blue room and behind the right should be the red one. Considering how they might both be similar to the current purple room, moving forward is most likely the safer bet.

To avoid a bit of potential future hassle, making a hole near the corner of a room could save effort if I plan on searching the adjacent room.

The plan is basically; make a small hole near the left corner of the back wall. Once I have a hole, I'll be able to decide if I want to remove the corner and gain access to not only the behind room, but also the blue room and maybe a potential diagonal room.

If I'm able to make an initial hole, a human sized hole shouldn't be much harder as I'd only need to remove four lines worth of wall.

****, I feel a bit dizzy, this is a bad sign...

My finger tips are still sensitive from the first pokes which makes the whole process so much worse. No one can understand the tediousness of willingly poking a hole in your finger, rushing towards a wall, squeezing a drop of blood out and then smearing it onto a wall. After the first drop comes a second, and a third, and a few more until it stops bleeding. Now reapeat this process for god knows how many times and spit on and scratch the wall every once in a while.

My throat is so dry...

I've made a mistake.

All that effort has gotten me a hole slightly wider than my thumb that's around 2 knuckles deep.

If I don't break through soon, I'll need to widen the hole and this might truly be the end of Jordan Joekepler. Why did I just think that?

The next choice is probably going to decide my fate. Continue trying to break through or switch to a different wall. The floor is almost certainly thicker than the walls due to stability reasons.

The other wall could be very thin, but that's just hopeful thinking. There's no reason for just one wall to be way thicker unless it's the outer wall.