Bevy 0.17 introduces this idea of "Messages" which mostly replace the
previous usage of "Events." The old events still exist, but are meant
more for targetted actions -- something happening and immediately
triggering a function call on an observer.
I'll be using this to make a sparkling effect on the debris field left
behind from a destroyed ship.
It can also be used to do the temporary invincibility effect when
(re)spawning the player.
Closes#16
Bevy provides Deref and DerefMut derives, so that's nice. I'm not sure
it makes any sense to keep the field private since those derefs expose
the Vec2 anyway. I added an `impl Default` anyway, though.
I'm not sold on the name, but anyway.
This module will hold the systems that power the main game mechanics, as
well as a few extra items to support that (in particular, the Lifetime
component).
