Thank you to Dan and Swampy for creating this show, and to all the writers, animators, storyboard artists, and voice actors for working so tirelessly to create something so wonderful. Now, on to the story.

So, in Act Your Age we find out that Phineas begins to like Isabella when they start high school, so I just wanted to explore how that might have begun (and if Isabella hadn't "given up"). I love fanfics of Phineas beginning to figure out his feelings, so I wanted to give it a shot. This is my first story ever, so please go easy on me. If you think I should continue with the story, leave a review! For now, it's just a one-shot. Also, sorry to all the Ferbella shippers out there. I honestly do love the Ferbella stories I've read, but for the show I still ship Phinabella. But hey, maybe one day I'll write a Ferbella story because I've read some really amazing ones. Anyways, enough blabbering, please enjoy!

I do not own Phineas and Ferb.

"Now that was the best day ever."

Phineas smiled, leaning back against his favorite tree in the backyard. He settled in, looking around at his friends as they sat quietly, letting the extraordinary events of the day sink into their minds alongside the beautiful setting sunset.

It truly had been an amazing day. It was their last 24 hours before summer vacation would end, so the ambitious brothers had of course pulled out all the stops. From the giant car with Ferris-wheels as tires to the life-size cotton candy trees to the rocket powered parasails, it had been incredible. It certainly was one of Phineas and Ferb's most inventive days, yet Phineas was honestly just happy to see the smiles on his friends' faces. Years ago, the contraptions he and his brother built had been completed solely to conquer the long summer days, squeezing out every last drop of fun they possibly could. But, as the years went on, Phineas had grown to simply want to make his friends happy while simultaneously enjoying their company. His version of hanging out with his friends just happened to involve backyard rollercoasters, combined seasons, and giant fighting treehouses.

"I can't believe summer's over." Isabella mused quietly, letting her gaze trail across all her friend's faces.

"Yes, it is a real shame." Baljeet chirped, trying (and failing) to sound saddened by the news.

Buford gave him a shove and rolled his eyes. "Yeah, ya look real torn up about it."

Baljeet sighed. "Well, can you really blame me? I mean, we are entering high school, people! Fresh pencils, new textbooks, advanced calculus…" Baljeet smiled and looked dreamily into the distance, content in his fantasies of complex calculations.

Buford gave him another hard shove as the rest all chuckled at their extremely math-enthused friend until Isabella spoke again, this time directly at Phineas. "Are you sad summer's over, Phineas?"

He looked up at her and shrugged, apparently still torn on the subject. "I guess so. But at the same time, Baljeet's right! I mean, it's high school! It should be pretty exciting, I hope."

The gang smiled at Phineas' optimistic and upbeat answer, nodding along at the true words.

"Besides, no matter what happens, we're still going to be friends! Just with a lot more homework," he added with a sheepish smile.

Everyone nodded to each another in agreement before lapsing into a comfortable silence, occasionally breaking the peace to bring up a favorite moment of the summer or past years. Despite the spontaneous trips down memory lane, it was plain to see that they all had other things in the forefront of their minds, most obviously the upcoming introduction into high school. Ferb chuckled quietly to himself, remarking how he had never seen his usually highly energetic friends so silent. But it had been a long (and fun!) day, and there was that thick, heavy feeling in the air of noticeable and impending change.

They all remained in the familiar backyard, drawing out the inevitable end of summer, until darkness settled and the stars began to twinkle. Finally, they stood, exchanging goodbyes and making plans to ride the school bus together, all agreeing that it would only be right to face this next step as a group.

The line of friends trickled out of the yard, Baljeet and Buford through the gate and Ferb through the sliding door, until only Phineas and Isabella remained. "You better head home, Izzy. Big day tomorrow."

Isabella smiled and nodded. "I know; I just don't want this day to end. Plus, I, I wanted to say thanks."

Phineas looked at her quizzically, "Thanks?" He thought back on the past few weeks but came up empty; he didn't remember doing anything especially noteworthy for her recently. Well, except for that huge sundae after her wisdom teeth procedure (since he never actually got to make her a giant sundae when she got her tonsils out years ago), but still, that had been more than a few weeks back.

"Yeah! I mean, it was a really great day. So, thanks for making it another wonderful one. Honestly every single day this summer was pretty extraordinary. Just like every summer," she finished with a small smile, looking up at him a little nervously, tugging at the bottom of her signature pink dress.

Phineas looked at her surprised, even a little taken aback. He knew that he and Ferb mostly did these summer activities for his friends, but they accomplished it all together, it wasn't just him.

"Oh, well, thanks Isabella! But really, it's a team effort. I mean, we couldn't have made those cotton candy trees without the Fireside girls' churning skills. I still can't believe there's a patch for cotton candy making."

She laughed, smiling a little at his Fireside patch confusion and his modest nature. She walked a little closer to him and shrugged, "Still, without your imagination and positivity, my childhood would have just been full of boring TV marathons and swimming in my pool. So, thanks. You and Ferb, it's pretty incredible what you two can do." She paused, choosing her next words carefully. "You're really amazing, Phineas."

Phineas simply looked at her, his jaw going slightly slack. Isabella had always been nice to him, I mean, she was one of his best friends! But he couldn't remember the last time she had shared such kind words. Well, that's not true. She always made sure to compliment him and Ferb's inventions, but she hadn't spoken about him like that since they were what, ten? He suddenly remembered them traveling around the world in a day and the end of that summer solstice. He smiled slightly at the memory of little Isabella hugging him and exclaiming over the success of the supposed impossible. But still, even then she had made sure to include Ferb in her complimentary words.

Phineas glanced up at her, noticing how the stars lit up her sleek, black hair that was tied back neatly into a no-nonsense braid, with a bow on the end, of course. Phineas had always secretly liked how she had kept the bow for all these years. It was so undeniably Isabella, plus it was pretty darn cute. It was a scientific fact, after all.

He suddenly realized that he hadn't said anything to her yet, and she had begun to look down, playing with her hands behind her back, nervous about the words she had permitted herself to say. Phineas swallowed, his heart beating a little faster, all of a sudden very aware of his sweaty palms and inability to grasp at words. "I, well, thanks Isabella. I, I mean, you're, well, I mean, you do all that with, with the Fireside girls and I do, stuff, and…" Phineas coughed, clearly flustered.

Isabella looked up in surprise, blushing, with a tinge of amusement creeping into her features, clearly enjoying the nervousness she managed to create in him. Although it was certainly intriguing to see the usually self-assured boy nervous and blushing, she wasn't the type to tease those who had been knocked down a peg, so she simply giggled and waited patiently for him to finish his thoughts. He finally swallowed and stopped wringing his hands, looking up at her and saying softly, "You're really amazing too, Isabella."

She smiled, a swarm of fluttering butterflies quickly erupting in her stomach, before reaching out and wrapping her arms around his neck, breathing in his signature scent of freshly mowed grass and power tools. Phineas paused, surprised at the sudden contact, then easily wrapped his arms around her back, taking note of the softness of her long braid, and enjoying the way it tickled his hands.

After a few more comfortable seconds of contact, she pulled away, dropping her hands from his shoulders, and beaming. "Well, I'll see you tomorrow, Phineas. Bright and early!"

Phineas nodded, waving as she went out through the weathered, wooden gate. "Yeah, see you tomorrow, Izzy."

She grinned at the nickname as she skipped home, unaware of the small smile on Phineas' face that remained for the rest of the night, even as he fell asleep, his last thoughts before slumber being that the best part of the day had been nothing else but that quick, yet poignant exchange between the two young teens.

Definitely the best day ever.