I just watched a video on first conditional and it says that we can we use the present simple, continuous or perfect tense in the IF clause. And it has given a few examples:
If I play football, I will be healthy.
If I am playing football, I will be healthy
If I have played football, I will be tired.
I have learned the first one in school but I have not yet encountered the second and the last one. What I don't understand is under what circumstances should we use the last two cases. The following are what I think:
For the second sentence, I am not playing football at present in reality, but I am imaging what would happen if I am playing football at this moment.
For the third sentence, I had not played football in the past in reality, but I am imagining what would have happened if I had played football in the past.
Is my understanding correct?
Here is the link which gives the above three examples. BBC learning english