Spatial Inventory
The single most load-bearing system in the game, documented in detail by programmer/co-designer Joel Mason in his 2022 Game Developer deep dive (Sources). The first prototype used a plain item list; it contributed nothing, so the grid replaced it and became the core mechanic.
Anatomy
A 7×9 grid with structure baked in:
- Corner cells are dead/unusable (the hull shape).
- Dedicated attachment cells: engines at the bottom, rods at the sides, lights at the top.
- Asymmetric placement rule: equipment can only sit on its attachment points, but fish and items can be placed anywhere — including over empty attachment points.
That asymmetry creates the game's loadout economics: leave rods at the dock for more cargo space, sell an engine for room (and go slower), skip lights entirely and gamble on daylight (Panic System).
One grid, seven systems
Mason's own summary: the grid simultaneously implements item storage, player health (damage occupies physical cells, destroying items and blocking placement until repaired; enough hull damage sinks you), skills/stats (equipment loadout), upgrades (hull tiers add cells), shop inventories (vendors are grids too — stock limited by space, not gold), inventory-management-as-gameplay, and environmental puzzles (placing item shapes in configurations to unlock secrets).
Inventory-as-health is the standout: taking damage mid-haul literally eats your profit margin in real time, which couples combat/hazards to the economy with zero extra UI.
Dev-reported design costs
Mason is candid that the system generated cascading obligations:
- Placement must be player-owned. The game may never auto-place; every pickup is a potential flow interruption, so the game's cadence has to tolerate pauses. His contrast case: Tarkov's spatial inventory under constant threat gives no room to enjoy optimizing. Dredge's chill sailing beats are what make grid-fiddling pleasant.
- Quest items need refusal flows. If your hold is full of eels when someone hands you a package, you must be able to decline and return — extra dialogue, quest logic, testing, localization.
- Quest items are destructible anyway. Otherwise a hold full of key items becomes an invincibility shield. Passengers can be lost overboard, and quests branch on it. (The dog is invulnerable.)
- Interaction edge cases: hot-swapping held items, exiting the UI while holding an item that no longer has a home, controller-friendly auto-move/swap-sides helpers, tooltips occluding the very grid you're arranging.
- Balance dimension: shapes are a tuning axis. The team had to guarantee players could physically mount enough engines to hit required speeds before specific monster encounters (Regional Design).
Design principle
A spatial inventory is only worth it if the game offers plausible pauses. It converts idle time into satisfying micro-play — but it taxes every other system that touches items.