What Makes N++ Different To Other Platformers?

This is The Mechanic, where Alex Wiltshire invites developers to discuss the inner workings of their games. This time, N++ [official site].

What makes Metanet’s long-running N series different to other platformers? Each level takes place on a single screen, and that makes it uncommon, but certainly not unique. It focuses on acrobatic avoidance of hazards, but that makes it an elder cousin to Super Meat Boy.

Instead, N is distinctive for its use of physics, or more precisely, its take on physics. Though it uses just three digital inputs: right, left and jump, the dynamic range of your little stick ninja’s movement is incredible, and just keeps expanding as you learn its nuances. The feel of N’s blend of low-gravity floatiness, inertia and lightness is irresistible, and Mare Sheppard and Raigan Burns have constantly been refining it from when the first game came out in 2004 to N++, which came out on PC just yesterday. And at the core of how its physics works is a single principle:

THE MECHANIC: Jumping adds velocity

In many platformers, from Mario on, the height of your jump is defined by how long you press the jump button. “Physically there’s no real way of doing that without cheating, right, because once you’ve left the ground you shouldn’t be able to change anything about your trajectory, but it’s more fun if you can,” says Burns. But N handles it very differently, and that’s because when Metanet began making it back in the early ’00s they were still students. They hadn’t made a game before and they had no idea how platformer jumps worked. They only knew one other developer in their home town of Toronto, Queasy Games, but they were on a mailing list on which the lead programmer of Halo had explained how collision and movement worked in that 3D shooter.

They also knew that they liked the approach a couple of games took to platforming. They liked the way you can slide and climb up walls in Super Bubble Blob, giving it a sense of verticality and space that most platformers achieve with flow- and control-breaking ladders. And they liked Soldat, the 2D deathmatch classic. “It was really inspiring for us because it was made by a then 19 year-old guy in Poland and we were like, we’re the same age as this guy and he figured it out so we should be able to,” says Sheppard. In Soldat you have a tiny jump, but you also have a jetpack with limited fuel, and if you jetpack right after jumping you can reach great heights. “It was this physics feeling of jumping up a hill and gaining momentum,” says Burns.

So, having taken direction from a physics-led FPS and two weirdo platformers, when you hit the jump button in N the game reduces gravity, and when you release it gravity is reinstated again. The longer gravity is reduced, the higher you jump, producing a very different feel to most platformers. “It contributes this floaty kind of somewhat out of control feeling when you’re in the air,” says Burns. “I mean good floaty. Floaty is a hard adjective!”

“You don’t really get a chance to fly around like that with the precision that we do,” says Sheppard. “Like, Sonic, if we can consider it a platformer, you for sure get that speed and you have a bit of momentum but you don’t get a chance to control it that much. We really wanted that feeling of fluid flying, which is very exciting, but you don’t want to get out of control.”

But it’s what happens after initially leaving the ground that makes N feel extra special. Most platformers give a set vertical velocity to a jump, and its length is often governed by the character’s horizontal velocity. But in N, instead of setting your resetting your vertical velocity to a standard figure when you jump, it adds to it. So if you’re already going up, jumping gains you vertical speed. With a good rhythm of jumps and using the level architecture just right, in N you can reach such great speeds and heights that you can cross the whole screen in a single bound, or impact the ceiling with such momentum that you die.

It’s a system that allows you to wall jump, quickly gaining speed as you rise if you can tune into the correct tempo of leaps. It also means that using the level geometry can make a huge difference to your movement, since the angle of the ground you jump from affects your trajectory: if you're running uphill and you jump, you get extra speed because the jump adds to your existing momentum. Moreover, if you hold the direction of the incline you’ll get a shallow jump, while letting go of a direction just as you jump results in your character leaping perpendicularly from it.

Chaining these different subtleties makes all the difference, because of the additive nature of your character’s momentum, where another jump builds on your speed and trajectory, rather than cancels it. “It’s sort of like a fighting game when you break down the input: a left-jump, a no direction-jump… You’re chaining these combinations of one or two buttons in a sequence to create a macro that’s not baked into the game, it’s something you perform,” says Burns.

“Yeah, so every input is affected by the one before it, each move is part of a chain and not an individual thing,” says Sheppard.

“You can see when someone crosses the bridge from being a n00b to getting the hang of it is when they realise that this jump they failed isn’t because of the last jump they did, they failed because three jumps ago they didn’t hit it right,” says Burns. “You have to realise your current range of trajectories you have access to is a product of what your previous movements were, which is definitely a lot more complicated and weird than most run-and-jump games. It’s definitely a bit of a learning curve, but that is directly what enables the game feel that’s so unique.”

And that’s where the challenge of making a game like N comes in for Metanet. While its physics system is entirely internally consistent, it can seem awfully counter-intuitive. N++ therefore features 120 tutorial levels. “You can speedrun them in like 20 minutes or something!” says Burns, but he concedes that for anyone else they takes a good hour. But they’re a fantastic introduction to the fathomless subtleties of this game, because they invite you to figure out each kind of jump and interaction yourself simply through level design. One example is a level that teaches the correct rhythm for wall jumps by shooting a laser down the wall with the timing of when you need to jump away.

“Actually it was pretty hard,” says Burns. “I’m glad we found that design because we have no idea how we were going to teach wall jumps until then. It’s hard to contrive because the moment is so fluid and you have so much range in your velocity. The player can really get around and it’s hard to constrain situations so there’s only one solution. That’s what makes the game so fun in the general case, that there are all these possibilities and you don’t know what the path is.”

One other important addition to N++ is frame buffering, a common feature which makes timing jumps a little more forgiving than it was in the past. Instead of only accepting a jump at the frame the game registers it, which might be after the ninja has past the end of a platform or before landing, it gives four frames on either side to pull it off. In a game built for 60 frames a second it means that instead of 16ms windows you get around 150ms. “It’s radically more but it’s still really, really fast,” says Burns, and it reduces the fiddliness of some manoeuvres, while retaining the tightness of the controls. Any more than four frames and it felt sloppy. “It’s super important that everything feels the opposite of sloppy,” says Sheppard. “You’ve got to know exactly where your character is at any moment so you don’t have to think about it, because you’ve got so much else to think about.”

It also brings pro moves, which in previous games required frame-perfect timing, into the realms of the possible. One such move is using the circular nature of the ninja’s collision shape to slightly roll over the corner of a platform, enabling the kinds of jumps you can pull off on inclines where there technically isn’t one. The result of making the core game easier to play has also meant the level design for the rest of the game has a wider range of difficulty, exploring the range of movements the ninja possesses and introducing new hazards and enemies. A notable one is the toggle mine, an explosive which allows you to touch it once, but once touched becomes armed. Reconfiguring space as you play, it forces you to change your movements in response to your previous ones. In fact, many of the enemies respond to your movements, such as evil ninjas that replay your actions a couple of seconds behind you and seeker missiles, so play is very much about controlling the level through the path you scribe through it.

But that probably wouldn’t be as fun if it wasn’t for the vast variation in movement that comes with those three simple inputs: left, right and jump. N is a game that you feel, a game about flying, about always adding velocity, about never, ever, stopping, and wondering how to get to that bunch of gold that seems impossible to grab. “It’s so distilled,” says Burns. “It’s just about movement, so it really made the game come alive to complicate the movement in that way, to add.”