The union of Scale, Gravity Ghost and the indie devs making them

Scale and Gravity Ghost share a surprising number of characteristics, especially considering how different their core mechanics are. They're both serene, soothing experiences, at least at first: In Gravity Ghost, players control a girl as she flows around the gravity fields of planets, searching for her fox, collecting stars and bits of the universe that were destroyed in a recent black hole. It's a physics game and an odd type of platformer, and it can be a simple exercise in circling planets or a completionist's dream, completely up to the player.

Scale is a first-person shooter, but the gun is a shrink-and-grow ray, allowing players to suck the size out of one object and blast it into other objects. Doing this, players can either complete esoteric challenges or simply play around in bright worlds of flowers, pretty houses, green grass and happy trees.

Gravity Ghost and Scale are made by Erin Robinson and Steve Swink, respectively, and both games were selected to participate in the PAX East and Prime Indie Megabooth this year. Robinson and Swink both live in Arizona, in the same city, in the same house, and they have been dating for four years. This month, they got engaged. To each other. See – so much in common.

I'll never get used to playing games with the developers watching my every move, but Robinson takes some of the edge off.

"You got that one really fast," she says as I circle the second planet in Gravity Ghost, just touching the star above it and leaving the level through a bright red door stuck to the top of the world. I could sit at our tiny corner table, Robinson's laptop plugged into the cafe's outlet, for hours, but we all have places to be, and I still have to play Scale. Plus, my parking meter is running.

I play through a handful of levels, collecting stars and learning new moves: double-jump and sprint, both classic mechanics that operate in exciting new ways when trapped in the gravity field of a planet, or dancing between multiple gravitational pulls.

It's not all tip-toeing through the interstellar tulips, of course. Gravity Ghost edges up in difficulty as the new moves are added, with one level placing me on a planet with a giant deer also rotating around it. Between the deer's antlers is a star, and I have to reach it. The catch is that the deer mimics my own actions, spinning clockwise if I do, stopping if I do, making it seem impossible to ever get closer to the star. The deer, however, can't sprint and can't double-jump – there's no on-screen prompt that outlines this phenomenon, but the player can figure it out, and will, after getting over the first wave of "well, this is impossible."

Robinson says she's surprised when people call Gravity Ghost a puzzle game, and so am I. It seems clearly to me to be a platformer, while Robinson thinks of it as a physics game. We agree that it lies in the nebulous realm where game genres overlap and meld together.

Gravity Ghost is in the middle of an art overhaul, replacing all placeholder art with finalized work. Robinson shows me a picture of all the different star systems and it's gorgeous, cartoonish yet polished, with clean lines and fantastical images. Robinson and Ivy Games were going to launch Gravity Ghost this year, around October, but she wants to flesh out the narrative, so it's been pushed back to 2014.

With 20 minutes left on my meter, Swink starts up Scale, another game that I could easily sink an entire afternoon into playing. The last time I played Scale, it was at GDC 2012, when the game was still in super-early alpha mode. Now, the graphics have been suped up, adding depth and shadow to the bright world, and it begins in a new environment. It's almost like a testing facility, a series of hallways where I learn how to pick up objects, and once I get the scale gun, how to shrink and grow items.

The scale gun itself has changed, and it will change even more, Swink says. It's designed as a scientist's experiment in magnifying atoms, a hodge podge of wires and tubes with a wrapping of thin gold foil around the middle. When I pick it up, the gun lets me know if I can't change the size of something with a panel that turns red and reads, "NOPE."

I take the gun to a level hub, where a series of worlds in large, transparent containers lines a pathway, each with a red button in front of it. I enter the first world and the environment is closer to how I remember Scale – bright and cheery, dotted with daisies and trees in green grass. There's a particle to collect, and using my brilliant sizing skills, I get it – literally, the screen says, "Particle get!"

It's a happy feeling in a happy world, but Swink says the game gets weird. The gun eventually becomes too powerful and sprays sizing juice all over everything, all the time, forcing the player to strategize and think quickly. As its development has evolved, Scale has become less of a puzzle game and more of an exploration game, Swink says, but there are still riddles to work out. The titles of the worlds provide the best clues for solving their puzzles.

Both Gravity Ghost and Scale are games to sit down with and absorb, which makes them tricky at conventions. This doesn't stop Robinson and Swink, of course: They famously and legally crashed E3 this year, setting up shop in the public halls, networking and showing off their games. Both Gravity Ghost and Scale were part of the PAX Prime Indie Megabooth, and they were kindly granted spots in the back corner of the booth, where there was still traffic, but less hustle and bustle than at the front of the booth.

"We had lines the whole time," Robinson says. "It was awesome."

Also awesome: The gold and emerald engagement ring Robinson shows off on her left hand, how they're still giddy about calling each other "fiance," and the fact that Swink wore red pants. Yes, those red pants.