The Witness is a game (which took about 6years to create) where you explore an abandoned island and solve the puzzles you find there. Some of the puzzles are easy, and some of the puzzles are pretty hard. If you ever get stuck, don’t worry; you can always move on to other things, and come back to whatever you were stuck on, later. In the meantime you might solve some other things that remind you of the thing that was blocking you, and this may give you ideas.
Watching videos or reading walkthroughs is highly discouraged, because the game is a very spoilerable game, and it’s very easy to accidentally see more information than you wanted, and ruin a “big surprise”.