Collision with another entity during a c_move instruction
or physics entity movement. The entity must not be PASSABLE and
it's push value must be 0 or less. On start of the event function,
the event_type variable is set to EVENT_BLOCK, the you pointer
is set to the other entity, the vector normal is
set to a direction perpendicular to that surface, and the vector bounce is
set to the direction into which the entity would bounce off.
The event function may now control the entities' make-way behavior.
If the hit entity now performs ac_move instruction,
it will not trigger a collision with the collider again when
the you entity
is excluded from the c_move instruction's
If two entities collide, each one's event function
can be triggered, the moving entities' one with EVENT_ENTITY,
the hit entities' one with either EVENT_IMPACT or EVENT_PUSH.
If both entities were moving, each one can get two different events in undefined