backpack will have several levels, each level add 3slots: example lvl 1: 6 slot lvl 2 9 slot lvl 3 12 slot ..... up to maximum slots
the backpack would be updated for raw materials (example 1000 cloth +50 ropes) each level would add a pair of slots + add a backpack pointer, how many slots are still available
the backpack would be updated for raw materials (example 1000 cloth +50 ropes) each level would add a pair of slots + add a backpack pointer, how many slots are still available