Learn Swedish: Medan ugnen blir varm, blandar jag degen. - While the oven gets hot, I mix the dough.

This is the V2 (verb-second) rule in action! The entire first part of the sentence (Medan ugnen blir varm) is a subordinate clause that counts as the first "block" of information. To keep the verb in the second position of the whole sentence, the main verb (blandar) has to come next, which pushes the subject (jag) to the other side of the verb.

Does blir varm literally mean "gets hot"?

Literally, it translates to "becomes warm". The verb blir means "becomes" and is the standard way to say "gets" when talking about a change of state in Swedish. The adjective varm means "warm", but in Swedish, it is commonly used for things we would call "hot" in English, like ovens, food, or the weather.

Both ugnen and degen end in -en. Do they follow the same rule?

Yes, they follow the exact same noun pattern. Both are regular "en-words" in their definite form (the "the" form). En ugn (an oven) becomes ugnen (the oven), and en deg (a dough) becomes degen (the dough).

Do I always need to use a comma before the main clause starts?