Implement UFO that tries to kill you

The original game had UFO's occasionally spawn.

The UFO would spawn on either the left or right side of the screen, and would move all the way across the screen horizontally at a constant speed before despawning once it reached the other side (assuming it did not get shot)

It would move up or down at random intervals somewhere between 1-3 seconds long.

It would wrap around the screen vertically.

It would shoot a laser at the player about once every second

It would die if it crashed into an existing asteroid