Tetris on ATmega328p (with shift registers!)

Below is a brief descripction of the Tetris project. The Tetris_v1 code was written by me and a few colleagues to familiarize ourselves with the digital electronics (the original version used MAX7219 displays so it was much easier to make). After building my version, I adapted the code to the shift registers.
The design is amateurish, the code is not 100% optimal (e.g. no header files, no structs, no enums, no typedefs) but it will not be improved due to the fact that it is a memento of our first project; the soldering is also not professional, but it was done to kill the spare time.

The Tetris_v2 code is a refactored version of Tetris_v1 (original). Although it is still not perfect, it is much better than the first version. The schematic and the physical connections remains the same.

Components used:

1. Microcontroller ATmega328p
2. Shift registers 74HC595
3. Led matrixes (columns - cathodes, rows - anodes)
4. Resistors, capacitors
5. Simple buttons

Schematic

Simplifications:

To make the schematic clearer, I simplified the pinout of the led matrices. You should assume that e.g. row1 and row1+ are internally connected.

Shift register schematics have been also simplified.

Full schematic:

(right-click + open in new window for better resolution)

(note: capacitors can also be added in parallel to the buttons)

Final product: