A timer built using the Adafruit Circuit Playground device; programmed in C and Arduino IDE. With this program, you can also build your own timer watch. So here is how you can do that?
You will need to complete your shopping list. You need to get the following items I listed below.
Adafruit Circuit Playground Express Edition -- (This is the board itself. The one that lights up.) https://www.adafruit.com/product/3333 LiPo Lithium battery -- (You could get a smaller LiPo battery at 350mAmps but I recommend the one in the link which has 500 mAmps as it has more power and lasts longer, and is the one I bought.) https://www.adafruit.com/product/1578 LiPo battery charger -- (to charge the battery, obviously. Plug battery in on one side and plug it to a USB port on your computer or anywhere that has one on the other side.) https://www.adafruit.com/product/1304
You also need to get some duct tape and some wrist band to turn it into a watch if you have some lying around.
You will need to download and install a program called Arduino IDE to your computer https://www.arduino.cc/en/main/software
Download this code https://github.com/crhodes2/Pomodoro_NeoPixel_Timer
Open the Arduino IDE program you've installed on your computer, and go to File > Open and go to my project zip file you download to access the .ino file you see there. The one called Project_Pomodoro_Timer. Open it, then plug in your Adafruit Circuit Playground board on your computer USB port. Finally press the Upload button on the IDE (the arrow button pointing right). Press it and the code will go into the board.
If successful, all the lights on your board will turn white and pressing the two buttons will make the colors change.
Congratulations! You got your own timer! :D