Research & Unlocks
Not every upgrade at the Armory is available from the moment you start. Some stat tracks and Cores are locked behind a research gate, bought once with Scraps to open that track up for good; some of those gates need you to have cleared an earlier one first. Weapon rarity is gated a different way — see The Armory — by how far up the Track Ladder you've climbed rather than by research.
This system is still settling — this page will grow as it does.