Puzzles and Multiplayer Rooms
Wikipedia has an entire entry on the mathematics behind Planarity, but you don't have to be a math geek to enjoy this puzzle game. Basically, it presents you with several points connected by straight lines; your goal is to reposition the points (which drag their connected lines in rubber-band fashion) so that none of the lines cross.
Planarity seems fairly straightforward when you start out with just six points. But the number of points and lines escalate with each level, and you'll spend quite a bit of time figuring out the puzzle as they climb higher into double digits.
Brettspielwelt means Board Game World in German, and this totally free (and ad-free) site is all about recreating board games online for real humans to play. Don't go looking here for Monopoly or Clue, however; the games are generally less commercial and more contemporary. Popular titles include Settlers of Catan, Carcassonne, backgammon, and the Asian classic, Go.
Brettspielwelt demands a certain amount of effort for newcomers. While you can play directly in a browser, things may go more smoothly if you download and install a Java client. Although by default everything is in German, you can tweak the settings to default to English (detailed instructions for doing this can be found on a Brettspielwelt tutorial Web site devoted to helping English speakers get up and running). While most of the players are German, they almost all speak at least some English--and there is a large contingent of native English speakers.
The games can be complicated, too--it's not easy to recreate three-dimensional game pieces and game boards for a two-dimensional PC display. But the graphics are pretty amazing, and if you find a board game you love (there's a list of the games on the Brettspielwelt site; click the small British flag on the upper right to get the English version), you'll love being able to play it online pretty much 24 hours a day--for free.
Have you ever played Pictionary? ISketch is a surprisingly sophisticated (and totally ad-free) Shockwave version of the game, where a group of players try to guess a word or phrase that one of them draws. The game randomly assigns sketching duties (ten rounds per game), and you know it's your turn when a set of drawing tools (simplified versions of palettes found in all image editors) appears, along with the word or phrase you're supposed to draw. You're awarded points for guessing the word that's being drawn (the person who gets it first receives the most points), and you also acquire points when people successfully figure out what word you're drawing.
Game play goes on in dozens of rooms that each accommodate up to ten players. There are rooms for different languages, and for specialty subjects such as movies or songs. Users are invited to submit their own word lists (at least 1500 entries are required) to form the basis of a new room.
The rooms have one pane for drawing, one for typing in your guesses, and another for chatting, where nothing you type is construed as a guess. Players police each other; people who persist in rude behavior, or who scribble words in the drawing pane, are often given the boot.
I stumbled across ISketch several years ago and was amazed by it then; I'm positively stunned that it's still running as a free game with not a smidge of advertising (as opposed to Shockwave.com's similar InkLink game)--and with even more features than I remembered. It's a true Internet gem.