Using Smalltalk (particularly Pharo) has been an eye-opening experience for me.
Its interesting to see that Amber has a Boolean class which I suppose corresponds to the JS boolean primitive.
In other Smalltalks, I've seen a wonderful design where True and False are subclasses of Boolean. This way, there are no conditionals in the implementation of ifTrue: and ifFalse:
Yes, it is a great appetizer. However, that there are no navigation buttons quickly becomes an annyoance. I once pressed a wrong key and had to select ProfStef next. 10 times to get back to where I was :(
One page (21?) seems to have a parsing bug.