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[Valter]

Inertia is a game term used to describe the time it takes to reach the maximum speed when a movement key is pressed, and the time it takes to stop when the movement key is released.

One odd tendency I've seen in most indie platformers is a heavy amount of inertia. A significant example is Cave Story, which is one of the most prominent indie games out there and also features fairly significant amounts of inertia.

What makes it weird, though, is that mainstream games almost entirely avoid inertia. The biggest platformer series in the indie market all didn't use inertia. Metroid,  The Adventures of Link (Zelda 2) had characters that started moving immediately and stopped immediately. Even in run 'n guns more similar to Cave Story, like Gunstar Heroes, inertia is absent.

So, for all of the programmers here who have made platformers, how did you handle inertia? Why did you opt to include/exclude it? Do you like playing games that feature heavy inertia? What do you consider to be the "optimum" amount of inertia to include in a game?

[The-Imp]

I actually enjoy the use of it, but I don't completely dislike no use of it.
Oh, and didn't Super Mario Brothers, 1 and 3 have some form of inertia? Along with Megaman 1 and 2?

[medieval]

Super Mario Bros had inertia

[Guert]

Maybe this'll help you a bit.
http://forums.tigsource.com/index.php?topic=1027.0

[Valter]

Controversial discussion topics removed.

[Matt Thorson]

A technique for good inertia:

The faster you're moving, the slower you accelerate.  I believe this is a technique used in the old Mario platformers.  Basically the formula is something like:

speed = speed + (acceleration * (x ^ speed));

Where X is some arbitrary value and 0 < X < 1.  This allows you to have the responsiveness of "immediate" acceleration from a standstill and the strategy involved with needing running space to reach full speed (and other design benefits of inertia).

My early games had no inertia, but with my recent games I've been experimenting with it.  Now I've discovered this technique and it feels great in action.  Looks like another "phase" for my platformers

[muku]

The faster you're moving, the slower you accelerate.

I think I have actually noticed this in your games, and it always felt a bit odd to me; once you are moving at a high speed, especially while jumping, it is very hard to decelerate enough in order to correct for a slightly too long jump, etc. I'm quite positive that this has caused me to miss literally hundreds of jumps (and die a horrible death) in FLaiL. I just couldn't get used to it, even after dozens of hours of playing it, and I think this game (and Jumper 3, which is the other one I've played extensively) would have been more enjoyable to me if that excessive inertia had been toned down a bit.

No offense is intended, these are still excellent games; why else would I have put so many hours into them. It's just that I often felt that tighter controls would have made me pull out my hair in frustration a bit less.

[Matt Thorson]

The faster you're moving, the slower you accelerate.

I think I have actually noticed this in your games, and it always felt a bit odd to me; once you are moving at a high speed, especially while jumping, it is very hard to decelerate enough in order to correct for a slightly too long jump, etc. I'm quite positive that this has caused me to miss literally hundreds of jumps (and die a horrible death) in FLaiL. I just couldn't get used to it, even after dozens of hours of playing it, and I think this game (and Jumper 3, which is the other one I've played extensively) would have been more enjoyable to me if that excessive inertia had been toned down a bit.

No offense is intended, these are still excellent games; why else would I have put so many hours into them. It's just that I often felt that tighter controls would have made me pull out my hair in frustration a bit less.

This feature isn't in either of those games.  Those games have linear acceleration (and deceleration, as you pointed out), meaning that no matter how fast you're moving, speeding up or slowing down always happens at the same rate.

I was aware of the amount of inertia in both of those games during development, but I guess that's just the kind of games i felt like making when i made them.  I really don't have any other explanation then that.  I'm aware it made those games very unpopular with some people (Jumper Three in particular was hated by a lot of Jumper Two fans for it), but it just felt right to me.  I understand completely how some people will find that frustrating but the game is what it is and the inertia is part of the design.

That said, my next project already feels much different, and uses the technique I described above.  However, it doesn't apply to slowing down.  So if you're running at full speed, it won't be exponentially harder to stop than at half speed.  The physics in my next game do feel much less "loose" than those in J3 or FLaiL.  Stopping is much easier and, because of the above formula, speeding up feels much more responsive.  Ironically, my next game has much more inertia-related mechanisms (variable jump height based on horizontal speed, etc), but the inertia itself is much less noticeable.

[muku]

This feature isn't in either of those games.  Those games have linear acceleration (and deceleration, as you pointed out), meaning that no matter how fast you're moving, speeding up or slowing down always happens at the same rate.

That's interesting. Hmm... I'm sure something about the acceleration/deceleration in these games felt strange to me, maybe it was the lack of the feature you described then; or just the comparatively slow acceleration. I can't put my finger on it, but something felt decidedly "nonlinear" regardless.

In any case, I'm looking forward to your next game, especially if it feels less "loose" which I think is more to my taste.

[Greg Game Man]

who cares?
Feel right in some games, and not in others.

[increpare]

Yeah, as soon as I saw this thread title I thought you of YMM.  The inertia in jumper 3 took a lot of getting used to (maybe I never got fully used to it).  I don't think I noticed it at all in flail.  Or maybe it's as much about the (relative lack of) friction as inertia J3.

I think it's cool that you're exploring more techniques now.

I hate the ragdoll-style/'physics engine' cum unresponsiveness school of inertia.

[muku]

I hate the ragdoll-style/'physics engine' cum unresponsiveness school of inertia.

Could you name a few titles in particular which this would apply to?

[increpare]

I hate the ragdoll-style/'physics engine' cum unresponsiveness school of inertia.

Could you name a few titles in particular which this would apply to?

http://www.freewebarcade.com/ragdoll-games.php, and this would be the canonical examples.  some people quite like that feel though.  More generally I'm talking about games that have dodgy physics engines....but...damnit I can't think of any off-hand.

[muku]

http://www.freewebarcade.com/ragdoll-games.php, and this would be the canonical examples.  some people quite like that feel though.  More generally I'm talking about games that have dodgy physics engines....but...damnit I can't think of any off-hand.

Ah, I didn't know that was practically its own subgenre.

I'm also getting pretty cynical about games which use a physics engine as their main gimmick. It was quite novel a few years back when these games started popping up, but nowadays it often feels quite formulaic. Besides, most of these games have this "physics engine techdemo" feel to them that is very generic and not very fun.

Then again, World of Goo demonstrates quite impressively that physics-based games can have wit and charm, so perhaps there is some good to come out of the whole thing.

But this is getting off-topic already, sorry

[Valter]

I made this thread with YMM in mind, honestly. He makes very difficult (yet fun! ) games that tend to feature large amounts of inertia.

I used to hate inertia , because it felt like an excuse for making the game harder without actually changing anything.

However, inertia really does broaden the possibilities for level design. Static movement allows for tighter control, but the jumps then become very simple, and it becomes difficult to increase difficulty without resorting to things like pixel-perfect jumps, invisible platforms, and other dirty underhanded developer tricks. Inertia really changes the way you run and jump. It allows you to make much more complex platforming in a smaller space. One thing that's always impressed me about YMM is his ability to fit a lot of stuff into a single room.