NUMBER CRUNCH COMMAND CENTER
Click the giant candy-colored buttons below like it is 2002 and you just discovered JavaScript tricks on a fan site.
This version now includes dramatic faux desktop error popups when the math goes off the rails.
PRO TIPS
Use your mouse like a true cyber wizard.
Percent and decimal buttons included for maximum bragging rights.
HOTKEYS 
Keyboard support works too: numbers, operators, Enter, Backspace, and Escape.