Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

I never was there, I am always to be.
You have never ever seen me, not ever you will.
Yet I am the confidence of everyone.

Who Am I?

What happened when the wheel was invented?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

I ask Joseph to pick any 5 cards out of a deck with no Jokers.

He can inspect then shuffle the deck before picking any five cards. He picks out 5 cards then hands them to me (Jack can't see any of this). I look at the cards and I pick 1 card out and give it back to Joseph. I then arrange the other four cards in a special way, and give those 4 cards all face down, and in a neat pile, to Jack.

Jack looks at the 4 cards i gave him, and says out loud which card Joseph is holding (suit and number). How?

The solution uses pure logic, not sleight of hand. All Jack needs to know is the order of the cards and what is on their face, nothing more.

Find the hidden panda in the image below.

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Find out which of the given views in the picture is accurately the top view of the given pyramid.

Spot 5 differences in two Christmas tree below:

You are trapped in a room with two doors. One leads to certain death and the other leads to freedom. You don't know which is which.
There are two robots guarding the doors. They will let you choose one door but upon doing so you must go through it.
You can, however, ask one robot one question. The problem is one robot always tells the truth, the other always lies and you don't know which is which.
What is the question you ask?