Complex sentence: The first three rounds were played as outlined above, except that the drawer's partners could not start guessing until the first 25 seconds was up; in addition, the drawer could not hand the marker off at the halfway point.
Split into simpler sentences: The first three rounds were played as outlined above, except that the drawer's partners could not start guessing until 25 seconds had elapsed. In addition, the drawer could not hand the marker off at the halfway point.