(this article was copied from this wikipedia article).
The main purpose of the game is to remove all cards from the tableau, assembling them in the tableau before removing them. Initially, 54 cards are dealt to the tableau in ten piles, face down except for the top cards. The tableau piles build down by rank, and in-suit sequences can be moved together. The 50 remaining cards can be dealt to the tableau ten at a time when none of the piles are empty.
There are several variants of spider, such as Relaxed Spider or Spiderette. The former doesn't require all spaces to be filled before redealing, while the latter is played with only one deck.
There are also three deck (Spiderwort) and four deck (Gigantic Spider) variants of Spider Solitaire.
The most common software version of Spider is the one included in the Vista, ME and XP versions of Microsoft Windows, Spider Solitaire. Another Windows version of Spider is Arachnid Solitaire. Arachnid is an extremely tricky game to complete successfully because a suit must be entirely completed before it is moved off the array, and there is not a lot of room to maneuver. Additional points are gained for keeping completed suits in play until all eight are complete. To make things easier for the novice player, the game offers an unlimited 'cheat mode' where moves can be undone right back to the beginning of the game, a partial cheat mode where moves can only be undone to the last deal, and a 'cheat-proof' mode where if you attempt to undo more than one move it changes the screen colour from green to purple and confiscates half your score.
On Unix operating systems, an early version was developed around 1989 at Sun Microsystems. A version of Spider Solitaire comes bundled with KDE for Linux. It is has been a part of kdegames for some time. Versions for Macintosh and most other operating systems are also available.
The Windows version offers three levels of difficulty, with one, two, or four suits.
Different software implementations of spider offer alternative scoring rules. The version from Sun Microsystems from 1989 defines the following rules in the manual: 10 points for each initially face down card that gets turned over; 15 additional points for each column where all the face-down cards have been turned over (even if you don't manage to get a space); 2 points for each card that is sitting atop the next higher card of the same suit; 50 points for each completed suit removed from the tableau (in which case you do not also score for the 12 cards sitting atop next higher cards). This yields a maximum score of 990. If you win the game with 4 or more completed suits still in the tableau, add 2 points for each suit after the first three. Thus winning with all eight suits still in the tableau yields a score of 1000.
In the Windows versions of Spider Solitaire, the scoring is calculated with a starting score of 500. One point is subtracted for each move; 100 points are added for each set removed.