How to Describe situations that didn't happen in the past

This video shows us how to describe the situations that are opposite of the future perfect tense. Here it is shown how to describe the situations that did or did not happen in the past using would, have and past participle. He gives us 3 very good examples that are describing such situations. In these examples he describes a situation which happened in the past which is actually a negative and uses a fact that is described in the present tense to give the reason why that situation ended in a negative note. One of the examples being taken is She didn't buy that car as it would have been too expensive. Here the situation is that she didn't buy the car, which is actually negative. And the reason for that is it would have been expensive. Here the fact is used to describe why that situation ended in a negative note. In this way you can describe situations that did or did not happen.