A simple countdown timer. Just enter an amount of time and press Enter.
It uses a natural time time display with a nice dynamic flipping animation.
I'd almost make the flippers into a library, but there's a slight bug.
It becomes very visible when disabling the animations
and especially when slowing down the interval at which the display is updated
because it only happens exactly when a change occurs and not the update after.
The bug can be "fixed" by disabling
display: table-cell; in main.css,
but this is used to vertically center the display.