The idea of using border to draw a triangle is to set the border value to a large value so that each side will appear as a quarter-block triangle. In this way, the triangle can be drawn directly without the help of pictures.
An example:
<!DOCTYPE html PUBliC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style type="text/css">#triangle{ height:0; width:0; border-top:solid 100px yellow; border-left:solid 100px purple; border-right:solid 100px purple; border-bottom:solid 100px yellow;}</style></head><body><div id="triangle"></div></body></html>
Effect:
If the width and height of the block are set, the edge effect will still appear. Each side will be an isosceles trapezoid, similar to a picture frame:
<!DOCTYPE html PUBliC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style type="text/css">#triangle{ height:100px; width:100px; border-top:solid 100px yellow; border-left:solid 100px purple; border-right:solid 100px purple; border-bottom:solid 100px yellow;}</style></head><body><div id="triangle"></div></body></html>
Effect:
Using this principle, triangles of different shapes can be drawn, for example Right isosceles right triangle commonly used on menus:
<!DOCTYPE html PUBliC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style type="text/css">#triangle{ height:0; width:0; border-top:solid 100px rgba(0,0,0,0); border-left:solid 100px purple; border-bottom:solid 100px rgba(0,0,0,0);}</style></head><body><div id="triangle"></div></body></html>
<!DOCTYPE html PUBliC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style type="text/css">#triangle{ height:0; width:0; border-right:solid 100px rgba(0,0,0,0); border-bottom:solid 100px yellow; border-left:solid 100px rgba(0,0,0,0);}</style></head><body><div id="triangle"></div></body></html>
Picture:
One more:
<!DOCTYPE html PUBliC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><style type="text/css">#triangle{ height:0; width:0; border-right:solid 50px rgba(0,0,0,0); border-bottom:solid 100px yellow; border-left:solid 50px rgba(0,0,0,0);}</style></head><body><div id="triangle"></div></body></html>
Tutu:
That’s it, come on! Make a little progress every day.