How my game over if red box hits yellow box

Question

https://code.sololearn.com/W5dX22wZATYy/?ref=app

Answer 1

Add collision testing in upo() and downo()
If posX > posY && posX < posY + yHeight
then do something.
If posY > posX && posY < posX + x Height
then do something

Answer 2

You must check videos related collision detection on YouTube.