Click Green Flag to Play. This is versus mode so you need to have at least 2 people to play. If you are the player, then you can use "arrow keys" or W.A.S.D to move. If you are the UFO, you will use the mouse to move, but every 1 second it will go to a random position or else you can easily one shot your enemy. You can click space for switching a mode.
The original project- https://scratch.mit.edu/projects/953568271
