Groups comparison

Upgrade system - 1986 to 2020
Has some sort of game mechanic to upgrade characters, equipment, or items.

Weapon upgrades - 1986 to 2023
Weapons can be linearly upgraded to perform better.

Permanent upgrades (Permanent research) - 1987 to 2016
Research, global upgrades and such from previous mission carries over to the next.

Upgrades: Abilities / Skills - 1987 to 2020
Player can upgrade or otherwise permanently improve the player character's abilities, making what they already can do more powerful, last longer or otherwise better.

Upgrades: Health - 1987 to 2015
Player can upgrade or otherwise permanently improve the player character's health.

Upgrades: Other - 1987 to 2015
Player can upgrade or otherwise permanently improve some unusual aspect.

Transient upgrades (Transient research) - 1994 to 2015
Research, global upgrades and such are lost after each mission.

Structure upgrades (Building upgrades) - 2003 to 2014

Upgrades: Carry capacity - 2008 to 2009
Player can upgrade or otherwise permanently improve the player character's carry capacity.

upgradesystem
weaponupgrades
upgrades-permanent
upgrades-abilities
upgrades-health
upgrades-other
upgrades-transient
structureupgrades
upgrades-capacity
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