A week later, a Royal messenger arrived with a letter sealed in pink wax.
Arthur opened it.
To the Dirt-Covered Genius, You owe me a trampoline. — Vivian.
Arthur looked at the calendar. "A promise is a contract," he noted. "Breach of contract damages reputation."
He gathered his materials:
High-Tension Steel Springs (Leftover from the mattress project).
Reinforced Canvas (Double-stitched).
A Steel Frame (Welded by Hammerhead).
...
Arthur traveled to the Royal Palace in the Steam Wagon (which now had springs and was much quieter). He set up the device in the Royal Gardens, right next to the Rose Maze.
It was ten feet wide. It stood three feet off the ground.
Princess Vivian came running out, trailed by her maids who looked terrified of the metal contraption.
"You came!" Vivian stopped, looking at the black circle. "Is that it?"
"The Pendelton Rebounder," Arthur introduced. "It utilizes Hooke's Law to convert gravitational potential energy into elastic potential energy, and then back into kinetic energy."
Vivian stared at him. "You talk too much."
She kicked off her shoes.
"Wait," Arthur stepped forward. "Safety briefing. Do not aim for the edge. Keep your center of gravity low. Do not attempt a double-backflip on your first attempt."
Vivian rolled her eyes. "I'm a Princess. I have perfect balance."
She climbed up. She bounced tentatively. Boing. Then harder. BOING. Then she laughed. It was a pure, delighted sound that echoed through the garden.
"Higher!" She shouted. "I can see over the hedge!"
Arthur watched from the ground, arms crossed. "Vertical displacement is approximately 1.5 meters. Acceptable."
King Roland appeared on the balcony above, sipping wine. He watched his daughter flying into the air, her hair wild, screaming with joy. He looked down at the boy standing stoically next to the machine, checking the bolts for stress.
"He built it," The King mused to himself. "He actually built it just because she asked."
Vivian stopped bouncing, breathless. She sat in the middle of the canvas, looking down at Arthur.
"It's... fun," she admitted, her face flushed.
"It is physics," Arthur corrected. "But yes. Endorphin release is a common side effect."
Vivian smiled. A genuine smile, not the polite court smile. "Thank you, Arthur."
Arthur felt a strange sensation in his chest. Arrhythmia? No. Probably just heartburn from lunch.
"You are welcome, Princess. Just... don't break your neck. The paperwork would be tedious."
End of Chapter 18