So I’ve been working on getting the upgrade system actually implemented into the game.
The upgrade menu can now be opened by clicking your character in the inventory panel. The various categories in the upgrade menu can be examined by clicking the arrows to the right and left of the category name at the bottom. The actual upgrades for each category can be examined by clicking the arrows under each upgrade animation.
The main guy in the upgrade animations is no longer nude, and instead he adopts whatever clothing your character is wearing.
Also, I’m about half-way done implementing all of the actual upgrades into the game. There are now special attacks you can perform, all kinds of stat bonuses, special items to get, etc…all purchasable with upgrade points within the upgrade menu. And in case it wasn’t clear, every time you gain a level from earning XP (by killing zombies, performing quests, etc), you get a new upgrade point you can spend in the Upgrade Depot.
The following animated .gifs demonstrate how the animated menu looks, and a few of the special attacks (special hand attacks, special 1-handed melee weapon attacks and special 2-handed melee weapon attacks)