Player and Atom collision

[beghelli]

Whenever an atom collides with the player without the player being able to collect it (see #8 ), then we have a player and atom collision.

The atom should behave like it is colliding with a neutron (see #7 ) (change direction based on its own direction, mass and velocity and the direction, mass and velocity of the player).

The player should spend energy to be able to absorb and support the collision, suffering the same physical effects that the atom.