Random Riddle: Two Gaps

Before a final time elapse
There will have been at least two gaps

During gaps, folks time they’re biding
While a dozen halt their sliding

When a certain red line is crossed
It means that you may have just lost

A masked man sometimes saves the day
Stopping projectiles aimed his way

The appearance of a red light
Brings both vexation and delight

What am I?

 

Random Riddle: Two Gaps