hey, i've got a project i want to work on and thought the arduino may be the perfect brain to make it work. however, i realized the project has 9 buttons controlling 9 leds, each button turning off/on a different set of leds.
can the arduino handle 9 inputs and 9 outputs?
yes, that should be no problem. A standard Arduino board has 18 available pins that can be used to detect a switch or control an LED. There are actually 20 pins (14 dedicated digital pins plus 6 analog input pins that can be used as digital) but two pins are connected to the serial port so these are not really available.
There are tricks you could use to share pins across multiple switches or multiple LEDs, but you won't need to worry about that for 18 digital input/output lines.
Have fun!