Electronics Newbie question concerning LEDs

i see i thought it may be limited by the number of fingers you could play with. sounds like a cool project.

you should take a look at PWM (pulse width modulation). this is a method of "strobing". you could also use external drivers as mentioned, or transistor buffers in between all of the LEDs.

with PWM, if you used a 4 bit counter you could have 16 groups of LEDs which would be on 1/16th of the time (or off of course). staggering the phase of each LED group would mean you'd have a maximum of 200/16 LEDs on at a time. the programming is still pretty simple.