Colossus on the other hand was a much more serious, adult-oriented film. It's motive, "to ensure man's survival, I will restrain man" it the most haunting line uttered by a cinematic computer since the HAL 9000 said, "I'm sorry, Dave."
Tron doesn't have that gravitas, of course, nor does it try to. It's an adventure story rather than a pensive science fiction with late 60's smarm.