Countdown is a monospaced display font inspired by the 7-segment LED numeric displays that became popular in the 1970s.
This font was designed primarily as a numeric display font, so emphasis is on enuring that the digits 0 to 9 are encoded along with the letters from A to F in order to allow representation of hexadecimal values. Aside from a very limited set of punctuation marks (which are often represented separately from the 7 numerical segments in common physical implementations of an LED display), no attempt has been made to alter the segments in any one glyph to make a representation of that glyph possible or more readable. Countdown stays within the bounds of what would have been possible with a typical LED display from the 1970s.
Where possible, glyphs have been included for the Latin alphabet, although some letterforms are not possible with a 7-segment representation. Where neither upper case nor lower case are possible, no attempt has been made to include the letter in the font; where both upper case and lower case can be represented, both are included and where only upper or lower case is possible, both upper case and lower case will render the same glyph.
In addition to the alphanumeric and aforementioned punctuation characters, there are a few symbols that are commonly used with numeric displays (degree and minus/hyphen symbols). See the included glyphs .png file for all of the included glyphs.
Countdown is packaged as a .ttf file, so it can be installed or used in an application. Use in an app will vary depending on the technologies that you are using to build the app.
The links below will detail how to install fonts on some of the most popular operating systems:
Install on Linux - I have included a link to the Arch Linux wiki, please see the documentation for your specific distro if you do not use an Arch-based distro.