The summer sun was already bright as a moving truck pulled into the neighborhood. A few houses down from the Flynn-Fletcher place, Dex Vandall hopped out, carrying a skateboard under one arm and looking around with a grin. His mom was already calling from the driveway.
"Dex! Don't forget to unpack your room before you go running around the neighborhood!"
"Yeah, Mom, I got it," he answered, though his eyes were already wandering. That's when he spotted two boys in the backyard a few houses away. One was hunched over a massive sheet of paper, sketching with excitement, while the other stood quietly with tools in hand.
Dex wandered closer, curiosity tugging at him.
"Hey," he called, leaning on the fence. "What're you guys working on?"
The redheaded boy looked up instantly. "Oh, hi! I'm Phineas, this is Ferb. We were just coming up with something to make summer even bigger."
Ferb gave a small nod, silent but approving.
Dex tilted his head at the design. "Looks like a theme park."
"Not just any theme park," Phineas said, his eyes shining. "An HD World! Every ride, every game, everything in high-definition holograms!"
Dex smirked. "You know what it needs? Stunt ramps. Coasters you can ride like a skateboard. Something extreme."
Phineas gasped. "That's brilliant!" He turned to Ferb. "I know what we're gonna do today!"
Ferb gave the slightest smile and lifted a hammer.
—
Within minutes the backyard was alive with the clatter of saws, drills, and rising machines. Projectors whirred to life while ramps unfolded like puzzle pieces. Phineas worked the blueprint, Ferb welded beams, and Dex hauled heavy parts with ease.
"Whatcha doin'?" Isabella called as she and the Fireside Girls trooped in.
"Building HD World," Phineas said proudly.
"Complete with stunt ramps," Dex added, giving the skateboard under his arm a spin.
Buford squinted at the glowing holographic coils rising into the air. "So what makes it high-def?"
Baljeet adjusted his glasses. "The projectors create a fully immersive experience using photonic energy! It's like standing inside a video game!"
Buford crossed his arms. "Sounds like cheating. I like my parks old-fashioned."
Dex smirked down at him. "Want me to save you a booster seat?"
Buford bristled. "I don't need no booster seat!"
Before the argument could go further, Candace came storming into the yard, Stacy trailing casually behind her.
"There it is!" Candace pointed wildly. "Stacy, you see this, right? They've got some kind of… some kind of HD amusement park growing in the backyard!"
Stacy barely looked at the machines, her eyes instead settling on Dex as he tightened bolts with a grin. "Mmhm. Yeah. Totally busted-worthy."
Candace groaned. "Stacy!"
Dex glanced over, catching Stacy's look, and flashed her a quick smile before hopping up on the half-finished ramp.
"Older birthdays get first dibs," he said, and launched himself into a smooth kickflip as the holographic coaster tracks spiraled into place behind him.
Phineas clapped. "He's like our extreme tester!"
Ferb, without looking up, murmured, "Or guinea pig."
Buford growled under his breath, but Stacy couldn't hide a small laugh. Candace tugged at her phone, dialing furiously.
"Mom! Mom, you've got to come home right now! The boys—and Dex—built a giant HD theme park in the backyard! I'm looking at it right now!"
"Uh-huh, that's nice, Candace," Linda's distracted voice floated back through the line.
Candace nearly screamed.
—
Meanwhile, somewhere across town, a very different kind of project was underway.
"Behold!" Dr. Heinz Doofenshmirtz cried, pulling a tarp from a bulky machine. "My High-Definition-inator! With this, I will magnify every pore, every blemish, every wrinkle, until no one can ignore me ever again! They will be too distracted by their imperfections to—wait, why am I doing this again? Oh, right. Because people don't invite me to birthday parties!"
His rant was cut short when a fedora-wearing platypus flipped into the room.
"Perry the Platypus! What an unexpected surprise!" Doof shouted, before tripping over a power cord as Perry advanced.
The machine sputtered ominously.
—
Back in the Flynn-Fletcher backyard, HD World was complete. Holographic roller coasters looped through the air, skate ramps shimmered with neon edges, and a giant wave pool splashed to life beside the treehouse. Kids poured in from all around the neighborhood, laughing and cheering.
"This is amazing!" Isabella squealed, holding onto Phineas's arm as a holographic ferris wheel spun overhead.
"Best first day of summer ever," Phineas agreed.
Dex dropped into a glowing half-pipe, twisting through the air with a perfect landing. The kids cheered. Stacy leaned against the fence, smiling wider than she meant to.
Candace tugged at her arm. "Stacy, come on! You're supposed to be helping me bust them, not swoon over Mr. Skateboard!"
Stacy shrugged. "What? He's good."
Candace fumed, eyes darting to the driveway. "Mom's almost home. Just wait until she sees this…"
But before she could finish her sentence, a sudden beam of light tore through the sky. The holograms flickered. The wave pool vanished. The entire HD World dissolved into thin air, leaving only a few scattered tools in the grass.
Candace blinked in disbelief as Linda walked into the yard.
"So, Candace," Linda said lightly, "what was it you wanted to show me?"
Candace stammered, waving at the empty lawn. "It was—! They—! But—!"
Linda smiled. "Well, I'll be inside if you need me."
As she disappeared, Candace let out a primal groan.
"Uggggghhhhhh!"
—
The kids lounged in the grass, Dex dropping onto his back with a laugh.
"So… this happens a lot?" he asked.
Phineas stretched his arms behind his head. "Every day of summer vacation."
Ferb nodded. "Sometimes twice."
Stacy gave Dex a sideways glance, smirking. "Not bad for your first day."
Dex smirked back. "Thanks. Just wait until tomorrow."
Candace buried her face in her hands. "Somebody stop me…"
—
Meanwhile, in a ruined lab across town, Doofenshmirtz dangled upside-down in a tangle of wires as Perry dusted his hands.
"Curse you, Perry the Platypus!