There are two ways of emphasizing a continuous tense in Swedish.
The first is by using two verbs.
"De sitter och spelar" -> "They're playing (while sitting)"
With that method, the first verb is usually one that implies position like Stå/Sitta/Ligga.
Another way is with "Håller på".
"De håller på att laga bilen" -> "They are busy fixing the car"