I'm going to have to spread my jam days out, I think. Not really in line with ordinary Jam rules but I'd rather finish the game than toss something away. I had no time to work yesterday or today, so this might be a '7 weekend-days jam' for me!
Anyway, here's an update on the game itself as of the end of the weekend, and what I have planned. I knocked together a quick cellular automata world generator, which I then tweaked after talking to Darren Grey (thanks Darren!) who gave suggestions about balancing the removal of walls, etc. I really like how it looks now:

I've also got some simple hitting-things-in-the-face code in, and chests which you can open to get items out of:

However, I'm overcomplicating my design. One thing Darren also suggested was to avoid worrying about complex combat systems and just use a one-HP system. So the new plan is to have a single, monolithic level that is many hundreds of tiles deep. But you have a limited line initially and can only go so far. Spend money on collected loot to gain longer lines, etc. etc. Hopefully the line restrictions will also make the combat interesting (as it's all about positioning since you only have 1 HP).
We shall have to see. I'm actually behind with real-life work too so not sure when I'll be working on it next!