GREAT!
You added the game over screen perfectly! Congrats, just wanted to add on one more thing, The play and character buttons in the start when hovered actually makes the button unreadable or unable to see the text visually, it would be great for the game to fix that visual glitch!
Also if your adding my suggestions :D , please add the destruction effects or some damage effect to the U.F.O!
I definitely think the game will be even better!