At the end of each chapter, you can access the shop to buy new weapons, sell unwanted items, and upgrade your existing arsenal. Upgrades improve stats like firepower, firing speed, reload speed, and capacity. Prioritize firepower for your main damage dealers and capacity for weapons you use frequently. Some weapons have exclusive upgrades that significantly boost their performance, often unlocking infinite ammo for that weapon on subsequent playthroughs.

Upgrade Priorities:
- Firepower: For primary damage-dealing weapons.
- Capacity: Reduces reload frequency, especially for machine guns.
- Reload Speed: Crucial for shotguns and magnums.
- Firing Speed: Improves DPS for automatic weapons.
- Exclusive Upgrades: Often provide significant bonuses or infinite ammo.