It was hot outside, so I just stayed inside and played games in a nice cool room all day.
It was too hot to be outside, so I just stayed inside where it was nice and cool and played games all day.
ーIt was hot outside, so I just stayed inside and played games in a nice cool room all day.
「外が暑かったので、一日中涼しい部屋にいてゲームをした」
in a nice cool room で「涼しい部屋で」
ーIt was too hot to be outside, so I just stayed inside where it was nice and cool and played games all day.
「外がとても暑かったので、涼しい部屋で一日中ゲームをした」
where it was nice and cool で「涼しいところ」
ご参考まで！
Since it was hot outside, I spent the day playing games in a cool room.
「外が暑かったので涼しい部屋で1日ゲームしてました」を英語で言うと、"Since it was hot outside, I spent the day playing games in a cool room." となります。この場合、「cool room」とは「涼しい部屋」という意味です。cool は文脈によって「寒い」ではなく「涼しい」と解釈されます。
もし本当に「寒い部屋」を意味したいときは「cold room」を使うことができます。
カナダ 
アメリカ合衆国 
