Past continuous for actions happening over a period of time in the past

The past continuous is used to describe actions which continued over a period of time in the past. This period can be expressed with a time expression or a clause with a verb in the past continuous tense. In this case the two actions were happening simultaneously:

I was looking for you all day yesterday.
He was staying in Rome that summer.
Were you sleeping during the speech?
My friends were enjoying themselves playing cards while I was studying in my room.