Quantity   Component name
1 × Arduino Pro Mini 3.3v 8mhz ATMega328P version Must be 3.3v - 328p version
1 × 128x64 OLED Display I2C version. Get the I2C version with 4 pins only Use I2C version with 4 pins only, not SPI
1 × Lighted pushbutton switch momentary switch
1 × CR2032 3.3v Coin Battery
1 × CR2032 Coin Battery PCB Holder. Get the slimmest, low profile one you can find
1 × 5x7 cm PCB board
1 × 220 ohm resistor
1 × 4.7k ohm resistor
1 × FTDI to USB for programming the Arduino Pro Mini. Might need header pins or wires to make the connection
1 × Soldering gun, solder, time, maybe some ultra micro thin conductive wire for PCB traces Misc parts and tools