Here's one such list of rules to help us define this concept...
Eat in the sukkah.
Sleep in the sukkah, unless it's raining.
If the sukkah causes distress (too windy or cold), you're exempt.
If it rains, you're exempt.
If you're sick, you're exempt.
(We're very practical people.)
The blessing for sitting in the sukkah is:
Blessed are You, our God, Ruler of the world,
who has made us holy with commandments
and commanded us to dwell in the sukkah.
I think playing your Nintendo DS counts as "dwelling."