quantity_point should be updated to mirror the latest changes to quantity and provide interoperability with other libraries (i.e. std::chrono::time_point).

It came up in #41 that it would be nice to have functions like abs(), sqrt(), etc. implemented on $System<f64, U> (and friends) directly, and not just through traits, so that they could be called without the traits in scope.

here's my Idea for a random mob spawn (Aggresive Mobs)

You could make it so that that mobs that already have a model ingame sometimes get re colored and have diffrent abilitaes or mixtures of abilites some mobs already have

An exemple of this could be a creeper who is purple and teleports to closetst player when in the sutible area for being seen and explodes.

but you could also make a wh