past tense verb
I saw that "use past simple tense when a time period is given " in a book. But It's different when I learned to the other.
If I had resisted the temptation of instant food, I wouldn't gain weight.
If I had resisted the temptation of instant food, I wouldn't have gained weight last night.
In this case, 'last night' is a time period.
But why does it put 'wouldn't have gained (have pp)', not 'wouldn't gain'?
I'm confused the differences.
please let me know when use have pp and just only verb.