A lot of work went into making RunGunJumpGun; its levels and each second of gameplay feel fair yet challenging. There are small things, like making levels "concave," so your character can't get caught in a cove and die, or ensuring the automated movement "is always the speed you want to go at," but the truly interesting tweaks are invisible.

ThirtyThree Games used analytics and testers to analyze every second of gameplay. "We let a lot of people play the game, and we could see these big spikes where everyone was dying," explained Bloemen. The team then acted on that data in different ways. Some levels were simply reordered for a smoother difficulty curve, but others were changed on a second-by-second level. "We collected the actual position where every person died," said Gilmour. "So we could see where everyone was being killed by one hazard, and then just take the hazard out."

The team would iteratively reorder and smooth out the levels, then bring in a new group of testers that hadn't played before and see what the new data looked like --its own little live, die, repeat loop, as it were. The importance of curving difficulty, according to the team, is paramount. "Especially the first world, that's kind of make-or-break," said Bloemen. "That's where you're going to piss someone off and they're not going to play anymore."

It's tough to find a better example of a difficulty curve done right.

While the first world (there are three, each containing 40 levels) hooked me, the second made me fall in love. It's there that the developers start throwing a bunch of new elements at you, and it's tough to find a better example of a difficulty curve done right.

Take the first 10 minutes or so of world two: It starts by introducing a new mechanic -- screen-warping, which allows you to fly out of the top of the screen and appear at the bottom, or vice versa. Then it asks you to use screen-warping to navigate a complex level. Then it makes you do that with pinpoint accuracy -- one false move, and you're dead. Finally, you've nailed it. Of course, before you have time to relax, turrets are added. Then force fields. Then spaceships that shoot at you. Finally, fire turrets -- the barrage of new elements feels like it never ends.

Removing the deaths, the section amounts to maybe three minutes of gameplay. In that time, you'll have learned and mastered multiple new mechanics and hazards. Although the deaths will come thick and thin, no single level transition is too challenging, But if you skipped any given minute, the leap in difficulty would be near insurmountable.

Later in the game, some of these new mechanics take a little longer to get used to. The addition of water, in particular, threw me off for a while, because the movement physics are completely different. The final few levels are also an exception, as the difficulty is pretty much just ratcheted up to 11. But the general curve and the way new ideas are introduced are nothing short of perfect.

While data obviously had huge impact on defining the game's structure, it wasn't always enough. The team had its own thoughts on how enjoyable or challenging each level was, and there's not a linear line of difficulty from beginning to end. "It's important to have a little bumpiness in that curve," said Gilmour. "Sometimes when we bring in a new mechanic, we make the first version of that a little harder. But you overcome it, and then the next time it's easier and you get a nice win, it feels like you're getting some mastery."

It also helps that playing the game feels great. The pixel art is bright and easy to follow, while the EDM soundtrack mixes menacing bass with light melodies that reminded me of another twitch favorite of mine, Electronic Super Joy. Like ESJ, rather than taking itself seriously, RunGunJumpGun is filled with humor. Some of this comes through dialogue -- there's a story told through one-liners before each level -- but a lot is down to the game itself. I lost track of the number of times I fell into an obvious trap, or a spinning disc bounced up at just the right moment to kill me -- there's a deviousness to the level design that, when coupled with the quick and colorful restart animation, actually makes dying as funny as it is frustrating.

There's a final piece to RunGunJumpGun I've neglected to mention, and it's perhaps the thing that'll keep you coming back: Atomiks, the game's name for the 10 tokens scattered throughout each level. Taking the "Atomik path" will bring you closer to death than any other path through a level, essentially making it "the nastiest way to play," according to Gilmour. A tone chimes when you collect an Atomik, increasing in pitch each time to form a satisfying musical scale.

They're almost like false waypoints, tempting you off the safer path at every opportunity. But collecting Atomiks is also the way you unlock more worlds, and "completing" the game is collecting them all. The path to victory is littered with near-endless death.

I played RunGunJumpGun a lot on a PC, and grew deeply attached to it. As such, I was a little worried about how the game would handle on mobile. There's a tactile immediacy about hammering away on a keyboard that's just missing from a phone or a tablet. But my concerns were unfounded. The simplicity of the layout -- tap the left side of the screen for jump, the right side for gun -- means that you don't miss the tactile feedback too much. I do think the game controls a little better with a keyboard, but being able to play it anywhere more than makes up for that.

"Personally, my favorite way to play it is on iPad," said Gilmour. "It's killer, the screen is really responsive, and you're holding this thing, it reminds me of playing a Game Boy when I was a kid." I have to agree. It's great to jump into for a couple of minutes at a time, or to completely zone out with for an hour. I've handed the game to a few friends, and even those who don't typically enjoy twitch games had a good time.

RunGunJumpGun is out now for iOS and will be released imminently for Android, priced at $2.99. There's been some talk of a PlayStation Vita port in the future, but that's very much in the "research to see if it makes sense" phase, according to Bloemen. Oh, and if playing on a PC or Mac is more your speed, the price of the Steam version will drop to $2.99 temporarily as well. In case it wasn't clear, whatever your platform of choice, I can't recommend this game enough.