button to control LED's ON/OFF & its brightness

After resting 4 2 weeks, i am back on my arduino journey. the new practice is about how to use button to control a LED's on/off and its brightness.

LED on/off is shown before, however, the interesting thing is setting the brightness by using the same button with PWM(pulse width modulation) concept. PWM is preset in arduino already. it is arrangement of the proportion of on and off to modulate the desired condition for brightness of LED or speed of motors etc.

it is a little exercise from chapter 5 in "getting started with arduino".