I have a plastic bag filled with coins, and wanted to know how much money was in the bag. I spent three hours writing this svelte-based website instead of just counting the coins in a few minutes.

• You can press the a, s, d, and f keys to increase the count of the quarters, dimes, nickels, and pennies. Pressing shift will decrease the counts.
• ...

This is written in a way that adding support for another currency / more coins should be easy. I'm not going to do that, but I'd be happy to help if you do :-)

I had $6.15.