Big patch, this one really starts to make the whole thing feel like a game.

- All enemies can attack you!
- Added bunches of sound effects
- When you die, the world regenerats
- The difficulty now ramps up over time
- You can pick and use potions
- Added the start of a little procedural town at the spawn point. It's a ghost town now, but I think it's the start of a neat system
- You can can xp and spend levels on the following upgrades:
    - Character speed
    - Item collect distance
    - Number of hearts
    - Reworked some UI bits

We still need to add ways to spend your coins (the procgen town is a start to that), and obviously we're going to need lots of other fun upgrades to get while levelling up. Still a ton of things that need to be expanded on, but I'm really happy with how things are shaping up!