Apple's state-of-the-art circa 1984. It's actually quite easy until the end. The last four pixels are ambiguous. The hint is that the right edge of the brushstroke is a straight line in column 23; no part of the brushstroke extends into column 24.
Nice one. Think I did it all using pure logic, although my brain might have filled in the odd gaps as my memory floated back to my first encounter with a mouse.
I remember trying to teach my Dad to use a computer for the first time. With a determined expression on his face, he picked up the mouse and carefully pointed it at the monitor like a remote control for the TV. At first I didn't know what he was doing. Then I laughed 'til I peed myself! I never let him live it down.
I never let him live it down.