What is a tedrad? Tetrads are all of the shapes you can make with 4 blocks. You are probably familiar with them from playing the game Tetris. If you would like to know more about them, see Wikipedia: Tetrad
What is this page? This is a silly page to show you some things that can be done with tetrads. If you have an idea for this page, please email it.
Phone passwords are often 4 digits, and tetrads have 4 blocks. This tool will choose a 4-digit number which forms the shape of a tetrad on a standard phone keypad. There aren't many possibilities, so don't use one of these for anything important!
Reloading the page will generate a new password.
This will pack some tetrads into a box for you. The filler script page will let you make your own.
The source code to my tetrad class for PHP can be found here.
These generated HTML tables are the same as the tetrads shown on this page. You will also need tetrad.css to style these on your web-page.