I need to know the name of a claustrophobic old movie, please! I’ve been searching for the name and the movie itself for 20 years.

It’s about three characters who are a family. That family discovers that they are trapped in their own house: the father hits the floor until he breaks it and realizes that the floor is blocked with a blue wall with the symbol of a “Z”. The same thing happens with the walls of their house which are painted with the same “Z”. Eventually they try to escape with a car they have in the garage but crash into the garage door and die of suffocation. In the end it is discovered that it was an extraterrestrial child who was playing with them as humans.

The movie has been made between 1970 and 1985, maybe produced in tecnicolor. Is an old school, classic movie. 

I think the symbol of the wall means the Zenith brand