Bryan Berg builds houses of cards — mansions of cards — and his Cardstacker Gallery has some astounding photos, including a record-breaking 25-foot tower.

When the Christian Science Monitor asked whether he could build a 100-foot tower, he said, “Sure. But it’s going to take a while.”

“I have to look twice before I move,” he says. “I basically go into slow motion.”

(A 100-foot tower could actually be dangerous. The 25-footer took more than 1,500 decks — about 250 pounds — of cards. “With something that big,” Berg says, “if it fell and you were near it, you’d run the risk of being buried.”)

Berg teaches architecture at Iowa State University, but he says his training didn’t help with the cards. Vice versa, actually: “I would even say that the majority of what I know about the structural behavior of real buildings and building materials came from my experiences building with cards.”

This spring will see the opening of the world’s tallest and fastest roller coaster. New Jersey’s Kingda Ka will accelerate to 128 miles per hour in 3.5 seconds, drop 418 feet into a 270-degree spiral, soar over a 129-foot hill and glide back into its station.

Statistically, roller coasters are actually safer than lawn chairs. But riders are drawn to the illusion of danger, and that’s spawning a new science of fear.

“We always try to make them look and feel more dangerous than they really are,” Michael Boodley of Great Coasters International told Psychology Today.

Good coasters exploit the universal fears of heights and falling. Riders want to feel a loss of control. “The closest thing to compare it to is driving with an idiot,” Boodley says.

Purists like rickety wooden coasters, where there’s a slow buildup and more time to fret about safety. “There’s a lot of self-abuse on that chain lift,” Boodley said. “Your own mind puts you in a state of paralysis.”

“LIMs,” the newer rides driven by linear induction motors, forgo that in favor of raw power, but they do exploit psychology by inverting the cars and suspending riders in space. (At Busch Gardens Tampa you’re actually dangled over a pit of live crocodiles.) And the very violence of a LIM ride — on some you’ll pull up to 4 Gs — is unfamiliar and thus scary.

Whichever your choice, your ride will probably last only a minute. That’s because the ride is accurately named: After the first burst of speed, the rolling cars are literally coasting.

I can make an airplane out of paper. Harold Gregg can make a Mercedes 320 SL, the Sydney Opera House, or the Taj Mahal.

See all this, and Gregg’s plans for the Louvre and the Crab Nebula (I’m not kidding), on his PaperToys site.