The indie roguelike Mysterious Castle may look simple at first, but beneath the minimalistic iPhone-adapted UI lies a surprisingly tactical party-based/turn-based RPG built with SRD 3.5 (i.e. a loosely Dungeons & Dragons-derived roleplaying ruleset) as the foundation and inspired by games like Temple of Elemental Evil, Tactics Ogre and Zangband. The roguelike part of MC is that the world is randomly generated, but unlike most roguelikes this is a party-based game in which the player controls up to the three characters at the same time. The combat gets complex and challenging really fast, and the often large-scale battles include things like enemy mages, AoE spells, summoned creatures and a mix of melee and long-range weapons with multiple attack options (such as snipe, rapid shots, flurry, spin attack etc.) as well as positional modifiers such as flanking and high ground.

At least for now, Mysterious Castle is first and foremost a Mac and iOS game for the mundane reason that the Hong Kong-based developer apparently doesn't own a copy of Windows. He would like to get the game properly ported in the future, though, but sales of the iOS version (as well as Paypal donations) will determine whether that will be possible or not. Planned features to be implemented in the future includes a much larger party of playable characters (presumably the SRPG inspiration has something to do with that), destructible environments and eventually even online play (!).

Official website:

http://www.mysteriouscastle.com/

indieDB project page:

http://www.indiedb.com/games/mysterious-castle

Developer's YouTube channel:

http://www.youtube.com/user/jjurksztowicz

Official trailer:

http://www.youtube.com/watch?v=c9gtLQGnjNg

The manual (good for getting an overview of the gameplay features):

http://www.mysteriouscastle.com/playerguide#quickinstructions

Here I was only a little while ago talking about Dungeons and Dragons requiring a tactics-style setup to be closer to the rules and here we have something that does just that.
 
I have my issues with 3.5 (I'm sort of hope these guys take a step or two away from the rules since the game was pretty much designed so that some choices were better than others, diminishing real customization options) but I'm really happy the developer's going with the SRD since most RPG vets are at least familiar with the basics. I get a thrill just watching that the combat unfold.  I imagine they'll change the names of spells around to keep things from getting weird. Here's hoping the PC version gets made, since that totally fits the crowd that would go for this.
 
I almost feel like there are too many projects to pay attention to, even within this narrow field. I THINK that's a good thing but I'd hate for good projects to be missed by people who would totally love to play them, or cool blogs that deserve more followers than they get!

I should've commented on this when I read it earlier, but after Temple of Elemental Evil I did think out loud how it would be a great idea if the Indie market took the idea of modular D&D adventures with that same strong core of strategic combat with the emphasis on the ruleset and just gone nuts with it. A roguelike's a fair enough compromise, since many of those modules still have weird licensing issues I guess (Wizards of the Coast aren't one for freely sharing intellectual property).

As a guy who doesn't own a Mac or an iProduct, I can only hope this reaches the PC. But then I've been buying Indie games all week thanks to the recent humble/royale bundles and the looming Black Friday Steam sale. I'm going to have to make my way through that lot first.

@ahoodedfigure: My own knowledge about the specifics of SRD is limited, but I do remember reading somewhere on the developer's site that he is quite prepared to experiment with the basic ruleset to improve the overall game design. Personally, my biggest worry would be that the game could perhaps go too far down the SRPG route for my liking by increasing the unit count considerably. I own copies of Final Fantasy Tactics and Tactics Ogre for the PSP but those plodding large-scale battles just don't appeal to me despite great production values and in the latter case a staggeringly ambitious storyline. Still, it's amazing just what a significant difference something as seemingly simple as height (i.e. a standard feature of the Japanese strategy RPGs which for some reason is rarely implemented in Western RPGs) makes to the overall combat experience.

@ahoodedfigure: Well, the unexpected joys of height implementation in a simple three character game like Mysterious Castle made me think about the fact that apart from mere conventions (and whatever licensed ruleset restrictions may apply) there's no apparent reason as to why the subgenre of small-scale, "non-Tactics" Western RPG (like TOEE or KotC etc.) couldn't implement height just as thoroughly as some SRPGs do. If memory serves me right, not even the rolling green polygonal hills of Wizardry 8 made much of a difference to the actual gameplay.

Part of what made FFTA so discouraging was they took out all the neat tactical features from FFT like height (they might've kept flanking and back attacks), falling damage from knockback attacks and having certain spells (like Bolt) do more damage against people standing on certain terrain (like water or metal). Presumably to make more room for all the angst and outfits with zippers and belts. Or rather because it was scaled back to fit on a GBA cart, but whatever.

After playing ToEE, where every encounter is carefully designed to be survivable for a level-appropriate party, I'm slightly concerned that might not be the case with this game and its more randomly-generated roguelike bent. Does it generate random encounters based on party level and challenge rating? Will it allow you to escape battles clearly beyond your prowess? Then again, "shit happens" is pretty much in the small print when you jump into a roguelike, so perhaps I should just knock it off with the wuss talk.

@Mento: The enemy unit count is alarmingly high even early on, and the only encounter modifier I know about is that enemies in caves and dungeons are even more brutal than those you meet in the outdoor areas (in this respect the old but free PC version (1.3) doesn't seem to differ much from the more updated iOS iteration (1.7)). Unlike "real" roguelikes there's no permadeath in MC, though, so reloading a saved game is always an option.