This is the system that launched the desktop interface revolution. By today's standards, Squeak looks somewhat crude and uneven. Scrollbars dynamically pop-out of the left side of text areas and lists.
Buttons are always square.
By working with Squeak, you have the opportunity to look at the starting point and compare it to whatever desktop interface you use today. All the surface features are there. But something very important was lost. All the code is there, plus examples, tutorials, and explanations built into the system to explain how to do it. While that's hard to grok in today's world, where a floppy disk holds more than an old-style disk pack, the meaning is still important.