Dice

The items of a set of dice carry a CollectibleDie: their number of sides, a colour and a material. Three kinds of sets suit dice: a base set every member gets on arrival, an earned set obtained for the site's points, and a paid set bought for oneself or as a gift.

DiceShelf::dice(member) lists the member's copies that are dice; choose(member, copy) makes one of them the die the member rolls for its number of sides — one choice per number of sides —; chosen(member, sides) returns its item, or null for the plain dice; clear(member, sides) goes back to them. A die traded away is no longer rolled: the choice falls back to the plain dice until the member chooses another.

tilttek/collections-bundle turns the chosen die into the appearance tilttek/dice-bundle shows. The appearance never changes the randomness.