Some GMs like to include puzzles in their games, which require the players to actually solve them to make progress. This is fine, but care should be taken to ensure the puzzles aren't too difficult for the players to figure out! It's surprisingly easy to make a puzzle way too hard, because the person making the puzzle knows how it works, and often ends up thinking certain things are easier to figure out than they are for someone coming in cold.

So if you want to include puzzles in a game, make them somewhat easier than you expect is required. And always provide some way to work around them if the players can't solve it at all. Pinning a Total Party Kill on the fact that the players don't know about some obscure property of prime numbers or something is verging on evil GM territory.

Transcript

Yoda's voice: Pleased to see that humility you have learned.
Luke: Awww, it was nothing.
Yoda's voice: A need to overdo it, there is not.
Luke: No, really, it was the opposite of Pride, and I'd already achieved Pride as the opposite of Humility.
Leia: Luke, what are you doing out here?
Luke: Vader can sense me here. I'm endangering the mission. I need to go confront her.
Leia: She's my mother too. Aren't I endangering it too?
Luke: She wants to pull me to the Dark Side. She's tracking me with the Force.
Leia: Look, I tried using the Force in the bike chase, and... I think it worked.
Luke: I can keep her busy while you lead the attack on the Peace Moon.
Leia: I should go with you!
Luke: And leave Han in charge?
{beat}
Leia: I'll stay here.