Tarm: Only 15 hours? That sounds short.
Any feedback you can give on the "Achievements to upgrade weapons" feature would be interesting to read.
omega64: Sounds like the Wolfenstein the New Order system except it actually unlocks gamechanging stuff like secondary firing modes instead of +10hp.
So here's how all the player progression stuff works.
There are upgrade bots in the game which will give you an attachment for one of your weapons. You get to pick the attachment, and every weapon gets two (except the pistol). When you have both attachments you can switch between them at any time.
There are weapon upgrade points which can be earned through the following:
1. Finding certain secrets
2. Doing the per-map challenges
3. Killing tons of dudes (there's a counter on the top of you screen that fills up as you kill dudes)
Those weapon upgrade points are used to enhance your attachments. For example, one attachment for the shotgun is a grenade launcher that turns a shell into a grenade. The upgrades are to decrease the cooldown, make it activate instantly (normally it takes half a second before it's ready when you pull it up), and increase the blast radius. You can pick those upgrades in any order, and they cost 1, 3, and 5 points for the first, second, and third upgrade taken. Once you unlock all three you can earn a master upgrade; this requires you to do an action a certain number of times. Sticking with the grenade launcher, if you get 20 direct hits on Imps you unlock a cluster bomb feature, where direct hits with the grenade spawn additional grenades.
There are suit upgrade points which are earned through finding specific dead soldiers (frequently in secret areas). This provide minor boosts. For example, you can get upgrades to take less damage from explosive barrels, less damage from your own weapons (i.e. reduce self splash damage), and finally no damage from explosive barrels. You have to take them in order in a particular category and there are four categories. The upgrades cost one, two, and three points respectively.
Finally, there are base stat upgrades which are found in the levels; it seems like it's going to be one per level (I only just started gaining access to them). These will increase your max health, armor, or ammo. Health starts as 100 max, armor starts at 50 max, and ammo is weapon dependent.