The Rules are simple:

• You are 'dealt' 12 cards, with various symbols on them.
• Your goal is find the 6 sets of 3 cards such that:
• The numbers of symbols (1, 2, 3),
  the colors (Red, Blue, Green),
  the shapes (Diamond, Oval, Triangle),
  and shadings (Solid Dark, Light, or Empty)
  are each all the same or all different.

To specify a set, simply click the 3 cards which make it up.

For example, this is a set:

Because,

• The numbers (1 2 3) are all different.
• The shapes (triangles) are all the same.
• The shadings (empty, light, solid) are all different.
• The colors (red, green, blue) are all different.

There are more examples below.

You can play the Set Game at the Official Site once per day, but frequently they have technical issues.

Another site, smart-games.org offers several varieties of game.

You can also buy a deck of Set Game cards from them or in bookstores or online.

This is my version of the game.

The graphics aren't as fancy here, but there are some extra features, and it's faster:

• Unlimited puzzles: just click New Puzzle to make a new one.
• Hints: if you get stuck, click the Hint button and it will tell what the counts are for the remaining sets: 111, 222, 333, or 123.
• No annoying popups to click away when you either find a set, or choose 3 cards which are not a set. (They go away by themselves.)
• Pause button allows you to take a break with the clock not running.
• Choice of two levels of difficulty: Easy and Hard.
  Hard allows variation on all four factors (color, shape, shade, and number).
  Easy makes one of the factors the same throughout.
• Average time taken over a series of puzzles.
• Times as you go along, not just at the end.
  I often find that I can find 5 sets very quickly, but the last one takes for...ever!