Preset Simple or Continuous

We can use Present Simple for things that happen time by time:

I play this game (every day)

We can use Present Continuous for things that are happening right now:

I am playing this game (now)

Also we can use Present Continuous for things that are happening in this period

I am playing this game (because for these 3 months I have someone to play with)

Then what is the difference between Simple(time to time) and Continuos for things that are happening in some period of time, if they can happen the same time to time.

In other words, what is the difference in some habit(Simple) and period of time(Continuous)?

If we have a house which we have been building for 26 years. We can say:

I build a house

because it's already become our habit(the time to time action)

And we can say:

I am building

pointing at this like at some temporal period of time, though it's for 26 years.