This is a simple count down clock where the background
changes from green to yellow (when warn 1 time is
remaining) and finally to red (when warn 2 time is
remaining).

This is intended for speakers to let them know how much
time they have left for their talk.


The count down is controlled with keyboard shortcuts:

[space] start/pause/resume count down

[r]     reset count down when paused or finished

[c]     change the total time, warn 1 time, and warn 2
        time when count down is reset