The real Terraria code isn't much better. Here's their 3MB [decompiled] NPC.cs: https://raw.githubusercontent.com/csnxs/Terraria/67de21a27e1... They had serious problems implementing multiplayer because they had to synchronize objects with 50KB of state every frame.
On the plus side, it's fun to press the page down and see the code 'animate' from left to right