New features:

There's a main menu.
There's an ESC menu (press ESC in game.)
Chunk generation happens on a separate thread so the game should feel a lot smoother.

Controls:

F11 fullscreen
R toggle mouse raw input
T toggle t-junction fixing
Mouse look around
WASD move around
Shift/space move up/down
ESC open main menu
N toggle noclip
P cycle polygon mode
[+ or numpad+] (press once or hold) increase render distance
[- or numpad-] (press once or hold) decrease render distance (without unloading existing chunks)
C toggle face culling
Left-click destroy block
Right-click place flowing water
F3 enable debug overlay
Scroll change block type (active block type visible in debug menu)

Used ImGui for my GUI.
Replaced my custom text-rendering shaders with ImGui.
All zmq messages are now sent across a single message bus.
- Pros:
  - Much simpler code. Every class gets a single BusNode object that they send/receives all messages through.
- Cons:
  - If a thread can't keep up and their incoming message queue overflows, they'll lose some messages.
  - Have to manually make sure any pointers I send are received, dereferenced, and deleted by exactly one thread.
  - Takes up a lot of RAM - I had to give all sockets huge incoming/outgoing message queues so that they don't miss any messages.
Ton of code cleanup
- Moved all .h code into .cpp
- Split complex classes into multiple ones
  - Focused on splitting away the rendering from the world data
- Replaced a ton of C-style pointers with std::shared_ptr

Perlin worms for cave generation
Separating the code more (I'd like to handle all GUI-related rendering in a separate class)
Pause world when in ESC menu
Importing and parsing Minecraft's model/texture files so that I can render all their assets without much repetitive manual work.