I recently took to thinking about complicated games.
Being complicated really limits your player base. For example, Dwarf Fortress is very complex. While its fans are very pleased with it, most people won't play it. Not out of disinterest, but because it's too damn complicated. It's not really a learning curve so much as a learning brick wall.
So most designers make simpler games... or do they?
The things we perceive as simpler games often aren't. For example, the gameplay of a first person shooter is usually taken in stride. But in actuality, this is extremely complex, featuring several kinds of health, cover management, ammunition, weapons with variants, zoom modes, special powers, secondary fire modes, health kits, weapon swapping...
The reason we don't see this kind of game as complex is because the genre has grown it. Any one game is just a little bit more complex than the game before it.
The downside to this is that anyone new to the genre will find the barrier to entry growing higher and higher. They don't have the history of the early games.
Now, one way around this problem is to make a game that is fairly simple at the low level but the player can create complexity. This is Minecraft's approach. Minecraft's early-game difficulty is mostly artificial. Once you understand the very basics of the game (the concept of gathering basic resources and a cheat sheet list of recipes) it's a pretty smooth learning curve as you figure out how to stay alive, build bases, and so on.
Once you understand this, you can start to expand your efforts - taking on monsters, creating traps, digging deeper, training dogs, trading with villages... these are optional tasks you can take on at your own pace and add complexity only as you see fit. The curve isn't perfect, and things frequently get bumpy, and the whole thing is derailed by creative mode, but fundamentally the idea is good. Add in complexity as you feel comfortable.
So I got to thinking: what if we designed our games that way for a while, but without the ugly bump at the beginning? One hidden gotcha to be aware of is that community actually drives a lot of this kind of thing - while some players will certainly experiment with the more complex and difficult elements of the game, far more players will do so if they see someone talking about how awesome it is. As an easy example, in Dwarf Fortress you can pump magma and create excellent magma traps... but it probably wouldn't even occur to many players to do that unless they read about someone else's magma escapades. Not because they're dumb or oblivious, but just because different players notice different things and draw different connections.
My most recent design is for a Power Rangers-style game, where you play geek and team manager. Your primary job is to create the gear that the rangers use with a fun pseudo-mechanical Turing-complete construction kit. The theory can be pushed really far - for example, having each suit able to direct power across to any other suit if they are in dire straights, or automatically kicking into overdrive when injured, or even pumping the right type of light into a ranger to calm them down if they start to lose it. And more that I haven't thought of, I'm sure.
But that makes it really complicated.
Rather than have a tutorial where I try to explain every element and how to use it, what if we embraced the idea of starting simple and letting players choose what complexities to tackle?
So you could start the game off just as a team manager. You don't even do any item creation - you choose the rangers, assign them colors and stock equipment. Set their training regimen, give them advice on how to deal with today's crazy situation.
You can get access to better stock equipment as seasons progress: you get better components, more funding, reverse engineer technologies, and acquire new power sources and devices during plot events. So it's just a wacky team management game.
But you can choose to tackle gear creation. Suits are the easiest - customizing the stock suits to fit each ranger's stat layout would be an easy first step, as would reconfiguring the suits to cause less stress to a particular character.
From here it's a relatively easy descent into more and more complex tasks, until suddenly you find you're building a starship for humankind's exodus, powered solely by the spirit guardians of ancient Mars or whatever.
In this case, part of the lure is just that the gameplay is waiting for you. However, I would actually make a big element of this the difficulty setting you choose to play on. Play on easy? You can keep going with just stock gear, it's okay. On normal you'll need to innovate some, because the the stock gear just isn't perfectly suited to your situation. On hard, you need to wring every iota of performance you can out of every device.
This can be reflected in the enemies. On easy, the enemies generally don't escalate. Even a few seasons in, if you fail to stop them, the repercussions will be relatively minor. On the other hand, on harder difficulties they race ahead to ever more threatening and terrifying levels. Still, those more powerful enemies are associated with weirder and more advanced resources, so if you want to play with the weird stuff, you've got to play on the harder difficulties.
A big part of this would have to be the community. Not only would people be able to share their rangers, devices, and episodes easily, but they also get to share their enemies. Show the most crazily overpowered randomly-generated enemy you encountered, and how he completely trashed your eleven-season 40-ranger team-up using their own children from an alternate future.
Anyway, the point is that I think it'd be a good exercise in design: designing a complicated game that doesn't have a big-ass tutorial or a giant barrier to entry.