It's a game for 2 players. There are 2 blue LEDs on top. Each player has 2 buttons - one for each LED. If you press the correct button when a LED lights up, you earn a point. If you press the wrong one, or do it before any LED lights up, you get 1s cooldown when you can't do anything. The LEDs in the middle from green to red are point tracks for both players. When you get max points + 1 you win. When a point track goes blank, it means that the cooldown is in progress.
Bear in mind that the current version of the schematic contains some mistakes (they are listed on top in the "TODO" section)!
Atmega328P with Arduino bootloader (Arduino UNO platform).
You can use the project as is - it contains platformio.ini, so it should build and upload out of the box.
You may copy the contents of main.cpp (except #include <Arduino.h>) and paste it to an empty sketch (.ino file) and it should work. Set platform to Arduino UNO.
Atmega328P doesn't have enough pins to drive each LED in the score tracks separately, so 2 simple serial-to-parallel shift registers are used to multiplex the LEDs in the score tracks. This means sending a pulse over each LED from bottom to top, one step per program loop cycle ("frame") until a desired number of LEDs has been lit, and then resetting the register for the remainder of the cycle. Due to the nature of this solution, it's crucial to connect the LEDs to the shift registers in the correct order. It's impossible to light up the score track LEDs in any other order (would be possible if a buffered register was used).
Even though the 2 top LEDs are connected to separate pins, they are still multiplexed to conserve energy from the batteries (the whole thing still draws around 100 mA at 3V battery input when all LEDs are lit).
The green-red LEDs in the score tracks use only 120 ohm resistors, because I wanted them to be as bright as possible (reaching ~20-25 mA of current) due to their short duty cycles caused by multiplexing over 8 LEDs in each track. The blue LEDs, on the other hand, use 1,5k ohm resistors, because they were much brighter than others in my case (even when there was no multiplexing). This has a benefit of conserving battery power.
The 2 UART pins allow for programming the Atmega via a USB-to-serial adapter, directly from your PC, without moving it to an Arduino board. Bear in mind though, that when your IDE starts uploading code, you must manually reset the microcontroller (using SW5).
For power supply I used a Pololu step-up/step-down voltage regulator with 5V output together with 2 AA batteries, but any other setup providing 5V on output will do, provided that it can handle up to 0,3W power draw.
Possibly adding some 0.1uF decoupling capacitors between Vcc & GND right next to Atmega pins could improve stability, but I don't think it's necessary in this particular build. No random resets were observed.
There's no nice OOP design here and no tests. There are a lot of global variables too. I'm aware it all could be nicer but I did in my spare time and the program is short. I hope the comments make up for the lackings.
LEFT SIDE DIP pin Arduino pin
top led l 19 13
shift reg clk 6 4
shift reg /r 5 3
shift reg data 4 2
btn up/left 15 9
btn down/right 16 10
RIGHT SIDE DIP pin Arduino pin
top led r 14 8
shift reg clk 13 7
shift reg /r 12 6
shift reg data 11 5
btn up/right 17 11
btn down/left 18 12