You can only carry the ammo you picked up, meaning you can't carry two types of items in your inventory. (twinfinite.net)
Depending on which character you use, you can only have 6 or 8 items in your inventory at once. (old-games.com)
You explore the island (a map lets you transport to previously visited areas), use items in your inventory to repair machinery and solve some fairly clever puzzles. (lifewire.com)