What is the simplest card game to play?

What is the simplest card game to play?
6 Easy Card Games for Kids

Go Fish/Fish. Object of the game: To collect as many sets of four as possible.
Old Maid. Object of the game: To avoid being the player who ends the game holding the Old Maid.
Concentration/Memory.
Snap.
Scumbags and Warlords/Rascals and Royalty.
Spoons/Donkey.

6 Easy Card Games for Kids
  1. Go Fish/Fish. Object of the game: To collect as many sets of four as possible.
  2. Old Maid. Object of the game: To avoid being the player who ends the game holding the Old Maid.
  3. Concentration/Memory.
  4. Snap.
  5. Scumbags and Warlords/Rascals and Royalty.
  6. Spoons/Donkey.