This is about why Flappy Bird was such a surprise hit, Taylor Swift’s newest mega-video is meh and why your favorite movies, novels and video games work when others fail.

Here’s why: audiences want something interesting, and entertaining, which means different and surprising. Yet there’s a fuzzy line between Hard and Impossible and a deadly chasm between Complex and Bizarre.

It’s like thinking, “chocolate chip cookies are yummy, so why not chocolate chip cookies with almonds, M & M’s, pecans, Oreo sprinkles, peanut butter and a Snicker’s Bar on top?”

Watch the big Taylor Swift video, BAD BLOOD, then we’ll chat.

Now, this has high production values and great costumes, and I’m sure Michael Bay watched it on an endless loop all weekend. Yet it’s not elegantly complex and entertaining. It’s a hot mess, the music video equivalent of THE EXPENDABLES, with so many random stars thrown in for cameos that I have no idea who’s who. Does it look cool? Sure. Do we care one bit? No. Not even half a bit, or a quarter bit.

Compare that to the simplicity and beauty of Iggy Azalea’s BLACK WIDOW, which is a masterpiece, paying homage to KILL BILL and flat nailing it.

Iggy didn’t need a cast of dozens. Notice how she starts slow and spends the first minutes with zero music at all, giving us the motivations of all four major characters right off. There’s a real story here. You actually care, THEN the music starts.

Also: it’s not like Taylor can’t do a great music video. She’s done tons of them. STYLE is far, far better and only has two characters. BLANK SPACE, two characters, great video. BACK TO DECEMBER, two characters, greatness. ROMEO AND JULIET, two characters, classic. Basically, Taylor should stick with two instead of two dozen.

Flappy Bird and the temptation of not-quite-impossible

We’re talking about an absurdly simple app, something a random dude put together in his free time, then became far more popular than polished games produced by people who MAKE GAMES FOR A LIVING, for monies.

Tap the screen and the bird flaps its wings and goes higher. Wait and it sinks toward the earth. Achieve the right balance between flapping and waiting and you’ll avoid homicidal green pipes stolen from Mario the Plumber.

Stupid, right? Except it’s just hard enough. Impossible to “win,” because there’s no winning. You just keep flapping until you smash into a green pipe and die. Yet that challenge made it a hit. Flappy Bird was just hard enough to be fascinating.

People will play games with horrible graphics and zero production values—if there’s a unique challenge to them. It’s not impossible, because nobody can win.

Professional game designers have figured this out. They’ll make games free to download, then tune the game so you can hit level 8 and almost, almost beat it … but it’s impossible unless you buy upgrades. And you’ll spend the $1.99 to do it, because things that are just shy of impossible are so, so tempting.

The same thing is true with great mystery novels and epic series like Game of Thrones, where half of the fun for the audience is figuring out clues, whether it’s who the murderer really is or what will happen in the end.

Make this puzzle harder enough—just shy of impossible—and people will devote entire blogs to dissecting every clue.

So people want to be surprised, and intrigued, by things that are hard and complex.

Related: You can pitch ANYTHING except quality

How this goes wrong

It’s easy for authors, screenwriters and game designers to cheat, to confuse Hard with Impossible and Complex with Bizarre.

Mystery authors do it when they give readers zero chance to figure things out on their own. Michael Connelly’s best villain is The Poet, who’s originally head of the FBI’s profiling unit. But the only clue readers get of this betrayal is … the man likes to rearrange the heroine’s desk in the FBI’s office to make it neater. No. That’s not a clue.

Directors do it when they go all David Lynch on an already complex story (Dune) and bypass Complex to head straight for Crazytown.

Literary authors and artists sin against the artistic gods when they create novels and paintings so obscure, pretentious and bizarre, nobody can understand them. That’s cheating, too, and it’s not impressive. I’m looking at you, Gertrude Stein.

This is also why traditional Hollywood endings are boring. We’re not surprised. There’s absolutely no mystery, no complexity. The hero kills the villain, utters a stupid one-liner and kisses the girl. Roll credits. Boring.

Then there are people who do it right. PRESUMED INNOCENT is a classic because there are enough clues sprinkled throughout the text to figure out who framed Harrison Ford for killing that pretty blonde Italian actress.

MEMENTO is certainly complex and almost impossible to figure completely out, but not quite. There are enough clues in there. Christopher Nolan played fair. He gave us what we wanted: an intriguing puzzle that teases us.