Working on a "gameplay performance" algorithm

Today started as a rainy day like so many others during this endless winter. Men, how i am sick of these....!

At least theses days were we are forced to stay at home are good for coding, so that´s what i did.

Working on my latest game "Surround It" i had the idea of implementing a "gameplay performance" algorithm. Basically since the idea of the game is destroy all the viruses, i came up with a simple algo to show the user upon Game Over... Depending on its perfomance during the game session, i show him how many days he would be able survive if he continued to kill the plagues at the same rhythm of the game session. This feature is only available on "Classic Mode"