After checking product availability, I made some changes to the schematic:

• The MCU is now an ATtiny3224. I don't need a lot of GPIO as I am using I2C components to interface with the buttons and LEDs.

• I've added a piezo and a 2N7002 driver FET for sound effects. I'm going to allow this to be disabled through a rocker switch

• I've switched the CP2102 to a FT230X. I tend to prefer FTDI's product portfolio and application notes.

• After some consideration, I've decided to switch everything to run off of 5V (as all chips on this board are 5V-compatible).
  • As a result, I've had to add a 74AHCT1G125 buffer as a level shifter to ensure that the 3.3V UART output from the FT230X can be read by the ATtiny (the ATtiny's Vih is 3.5V @ 5V, which requires level shifting).
• I've decided to remove the graphic display from the design. I thought it would take away from the goal of the game - to be a simplistic version of electronic mancala.