Got it from here: http://apps.eky.hk/css-triangle-generator/ http://apps.eky.hk/css-triangle-generator/ Here's a series of examples showing how it works (not a

Got it from here: http://apps.eky.hk/css-triangle-generator/ http://apps.eky.hk/css-triangle-generator/ Here's a series of examples showing how it works (not a fun animation like the OP, but a little easier to follow): http://jsfiddle.net/X8gXS/ http://jsfiddle.net/X8gXS/ Basically, you can get any triangle as long as at least one of the sides is horizontal or vertical.