I packed as many features as I could in it. 

The features that I actually wanted to use myself. My philosophy when it comes to making things like that is to constrain every aspect of development so the choices are easy and the process is systematic. And then, to maximize the use of every part that made the cut, to not waste anything.

The constraints I set up for it were:

- Standalone unit, no external reliances
- Mechanical controls, no touchscreens anywhere
- Modular design, repairable/modifiable 

The full build write up is available below with pictures, videos, and source code. 

Here is the brief of CinderClock's features:

- Alarm clock
It sets alarms. 

= Simple one time alarms like on your iPhone. 
Example: 06:00 AM

= Repeating alarms, that repeat on certain days or intervals, indefinitely. 
Example 1: 07:00 AM, weekdays. 
Example 2: 08:00 AM, every 3 days. 
Example 3: 09:00 AM, only on Mon, Tue, Fri. 

= ON/OFF duty cycle alarms, that repeat on certain days or intervals, following the ON cycle and OFF cycle. 
Example 1: 07:00 AM, 3 days ON, 2 days OFF.
Example 2: 08:00 AM, weekdays, 2 weeks ON, 1 week OFF. 
Example 3: 09:00 AM, only on Wed and Sat, 3 weeks ON, 1 week OFF.

= Sun following alarm. My favorite.

Enter your coordinates (or eyeball on the world map image) and it automatically calculates the local sunrise and sunset times.

Set your sunset/sunrise alarms with custom offsets.
Example 1: Sunrise, 05:31 AM, offset -00:30, thirty min before sunrise.
Example 2: Sunset,  07:18 PM, offset +01:30, one and a half hours after sunset. Go to sleep reminder. 

Each alarm has its own volume and ring sound. Choose from preset sounds or upload your own to the SD card. 

- Pre-alarm
Play smooth soothing sounds to prep you for the main alarm. 

- Timer
Simple timer. 
Example: 00:30:00 thirty minute timer.

Pomodoro timer.
Example: 25 min work, 5 min rest. 
Example: XXX (custom) min work, YYY (custom) min rest.

You can save presets for both.

- Stopwatch.
Simple stopwatch with centisecond display and laps.

- Calendar.
Simple calendar with full month display. Also shows alarms per day (up to 4) so you know on which days you have alarms set up. 

- Ambiance
Play ambient sounds to set the mood with custom animations like fireplace or rain. Choose from the presets or upload your to the SD card.

- Games
It has simple arcade style games like Pong, Maze, and Space Invader adaptations. Right now there are 8, more games can be added later.

Also, games can be used as an alarm dismissal option. Win the game to turn off the alarm, lose and try again in 5 min. 

- Settings
An extensive settings menu with top level controls. Includes details like:

= Choosing a standby face
= Master volume
= Sound effects
= Toggle display of additional features (temp, humidity, battery, alarms, date)
= Screensaver options

And more.