Many had a premium rate phone line, and it was just a tape so if you were stuck near the end you'd have to listen to the end and potentially pay many times the game's cost.

"Moon logic"

The puzzle were often moon logic or 'oh shit! You mean THAT is what I must do?'

Sierra online had great games with great stories and characters but their puzzles were... Yeah...

Nah! We were just tougher back then!

Also, with no internet, nothing was around to distract you for 24 hours, or days, to try to solve one puzzle.

Kids these days don't understand the struggle!

😃

I had to look up a solution in Myst because it was something I didn't know I could do.

There were also the "feelies", which were a secondary line defense of copy protecion method. They sometimes were a clue to those puzzles.