Follow the sandbag, and punch it using light attacks (L Key) and heavy attacks(H Key)! If you reduce its health to zero before the time is out, you win! If you don't, you lose(dun dun duuunnn!)! Right and left arrow Keys to move!
In case you're wondering, yes, I did get the sandbag idea from Super Smash Bros. Everything else was made by me! Except the background. I got that from Google.