you only have 2pwm and 3analog in's or made to be dig out / inbut... you're limited to size of program less mem, flash etc.. oh and there's not uart support on the attiny85..for more pins you need shift registers.. if you did attempt it
What part of the Arduino functionality would you like to keep?At a minimum you need:the '328P16 MHz crystraltwo 22pF caps100nF caps on VCC, AVCC pinsusing analog? need 100nF cap on the Aref pin10K reset pullup resistordiode such as 1N4158 across the resistor (anode to reset pin, cathode to Vcc)optional:Header pins to connect FTDI Basic/FTDI cable, and 100nF cap to connect to Reset pinorheader pins to connect to ICSP header for rebootloading or for installing bootloaderless sketchesplace to connect 5V wallwart, or a battery, or a 5V regulatorHere's an example for a ATmega1284P type board, a '328P would use a smaller connectorThis one has both FTDI and ICSP headers, but does not have the diode.It has screw terminal for bring in 5V power from a wallwart or 4.5V from a triple-AA battery pack (I've used both)
Ok, here it is, somewhat crudely drawn, have better tools at home.Not much is really needed.
Would i not be able to use the ATmega328 with the bootloader loaded?