The show maintains a lighthearted, comedic tone, and focuses on their adventures and their shared enjoyment of summer. It's also worth noting that, while their feelings are implied, the show avoids any explicit romantic themes.
However, there are numerous scenes where they express their affection through other gestures, like:
* Isabella frequently expresses admiration for Phineas's inventions and creativity.
* Phineas often relies on Isabella's support and encouragement.
* They share a lot of high-fives, smiles, and friendly banter.
Ultimately, their relationship is one of strong friendship and mutual respect, leaving room for interpretation and audience imagination about the nature of their feelings.