Some people are fascinated about spreadsheets. This lovely type of software was offered in Apple II computer back in 1979. Every cell could contain either data (text, numbers) or formula. What’s so special about it? Formulas are reactive. And that introduces the idea of reactivity.

Let’s have a look at few examples in some experimental technologies touching this idea.

Today many games need tutorial. Tutorial is a hot topic for discussion in indie games community. Anyhow, for programmer-non-designer tutorial implementation is just a job which comes with unwanted problems. Most of them appear because it tends to be made in the end of project. And worst situation is when tutorial is being done incrementally.

I will not discuss topic of tutorial design. Instead I’d like to present some notes about coding a tutorial in online game which are derived from my experience and observations. In the end I’ll give my advices for coding tutorials.

Today I asked myself - how to use Memento design pattern to store object state in a more safe and effective way? Of course by automating some things using some base implementation. Read about why I needed better Memento and how did I achieved nice combination of Memento and Command design patterns. Full code is given.