Referencing a button in script for different game modes in the Space Shooter Tutorial

I've been able to get the Hard Mode working by essentially copying the original GameController object and changing the values. Upon clicking the Hard Mode button the original Game Controller becomes inactive and the new Hard Mode (game controller) becomes set to active). I would like to use t$$anonymous$$s same method for a score blitz mode where the player scores as many points as they can in 1 minute. To do t$$anonymous$$s however i need to include a timer in the GameController script but i'm not entirely sure how to reference the Score Blitz button so that only when that button is clicked the timer will start.

   As a side note i've attempted to make separate game controller scripts for each mode but it breaks the game in too many ways to count. Can someone point me in the right direction here? Thank you!