Some notes on Play and Its Role in the Mental Development of the Child by Vygotsky:
- Defining (child’s) play through pleasure is not correct for two reasons. 1) there are activities that gives much direct experience of pleasure than play, and 2) there are games that do not afford pleasure or that are often accompanied with displeasure.
- Young children tend to satisfy their desires immediately. Without development at preshool years where needs cannot be realized immediately there would be no play. Development of play is connected to intellegtual and affective development.
- Imagination is play without action.
- Play can be discriminated from other types of activities by role of imagination; in play a child creates an imaginary situation.
- Play imply rules.
- “[E]very game with rules contains imaginary situation. For example , what does it mean to play chess? To create imaginary situation. Why? because the knight, the king, the queen, and so forth, can move only in specified ways; because covering and taking pieces are purely chess concepts; and so on.”
- Acting based on imagined situations teaches a child to guide decision-making not only by perception but also by the meaning of a situation.
- In play a child needs to create structures meaningobject; meaning determines her behaviour.
- It is inccorrect to thing play as activity without purpose.
Petri Lankoski 
Petri, if you want a good second look at the themes presented in Vygotsky’s book, try to get a copy of D.W. Winnicott’s “Playing and Reality”. In my opinion, it is one of the key works on play as far as game (especially roleplay) research is concerned.
When browsing my bookshelf I noticed that there is chapter “The role of play in development” in Vygotsky’s book “Mind in society”. The source text is the same with the referred web site translation, but I prefer the book translation. Basic stuff, nevertheless, is the same in both. I need to reread whole book…