A short project that can be modified by other users. Once the code is uploaded, TM1637 will display 00:00, after that you can use the 4×4 keypad array to type how long the timer should go (4 digits should be pressesed, 5th press will trigger the countdown, you can press anything for the 5th one). You can use the function at the bottom of the code to modify the result once the timer ends. Note: No code for the letters parts (outer right side of the 4×4 keypad) yet. bugs might be encountered when letters are used.