When your only option is Java or C++ I have the following thoughts for you:
Android supports C++ via NDK; PC and iOS support C++ (there are some free systems that support mac, pc and ios e.g. http://www.maratis3d.org); Java works for PC and Android (there are some free systems that are build for this like libGDX); there are some free systems to compile Java/Android stuff to iOS (http://www.xmlvm.org/ -> http://www.cokeandcode.com/aboidblog/ ); AFAIK all these "compile to XY" solutions are not production quality systems;
some commercial systems support all devices (e.g. unity);

I personally would try to develop with Flash/AS3 (see http://www.gamedev.net/page/resources/_/reference/programming/game-programming/300/developing-a-mobile-application-with-flash-r2797 ).

The added bonus to performance is especially important to game developers.

I would say: productivity over performance.

Giving HaXe a try might be a good idea. I never used HaXe yet. I'm afraid that it is still very hacky and backed only by a very small community... HaXe seems to be something that rarely works out of the box and requires quite an understanding of the target platforms/languages - this is why I would never recommend haXe to total noobs.
Btw interesting similar project by google: http://code.google.com/p/forplay/

sorry for this OT stuff...

ps: i am interested in good benchmarks, can you point me to some?

Isn't Flash itself very crossplatformish? I guess targeting iOS is easier with Flash than with HaXe. http://www.gamedev.net/page/resources/_/reference/programming/game-programming/300/developing-a-mobile-application-with-flash-r2797 seems to be a good introduction. Scaleform seems to be able to bring Flash even to XBLA, PSN and WiiWare. Some Games on Steam are made with Flash/AIR too... When Molehill is ready, there is no need for any other system than Flash and some nextgen engines ^^.

Bothering about such things only slows your production speed. Unless you are making nextgen stuff or games for weak devices (like old cell phones) you can do as you please. Beware of premature optimization.

The rooms may have pocket spaces that are only accessible from other rooms. The question then is, "where do I start a flood fill from?"

player start position or portals... the floodfill could just flood through the rooms like the player would. it should be able to "flood" through portals like the player... don't tell me you cannot distinguish holes in the wall from room entries/exits...

*custom floodfill knocks at the door*
when doing this you could run over the grid afterwards and remove all tiles that have no empty neighbor.(for very similar results to your algorithm) (btw using floodfill would also assure that the player cannot leave the level through a hole in the wall...)

I loooove every level in DKC :D I was so disappointed when I found out that there is no water level in DKC Returns. What issues with hitboxes?

Yeah. Donuts are an issue.

But this week we also tried one of the advantages of connecting rooms by matching up exits, Making a room that fits inside a donut. That was pretty cool. In such a situation, not illustrating holes might be an advantage because it wouldn't add the hole in the middle to the player's progress map until you went inside it.

then your solution seems to be a good fit . btw thx for sharing the code. maybe you can implement a mode where the automatic detection is skipped and the editor can place "minimap border pieces". this would lead to full flexibility. in special cases the artist could augment the automatic result or just skip it for hidden rooms.

I still don't understand how I'm supposed to go from a glow filter and fill in the result. Don't I still have to detect what the inside of the level is?

Yes, this is the main problem. I always thought you can distinguish inner parts of the room from the outer walls. Without this knowledge "draw everything with an opaque constant-colour on top, so that only the external edges are left" is impossible. I think a custom floodfill that "understands" portals should solve this and can fill the rooms.

Your Marching Cubes algorithm does not work for rooms with a hole in them/hides the hole, am I right?

Code:

  #################
  #               #
  #    #######    #
  #    #     #    #
  #    #     #    #
  #    #######    #
Start            Exit
  #################

Hehe I was aware of it, naming links often helps against this

I think this is much more interesting:
http://code.google.com/p/forplay/ (by google)
(similar to haXe)

AFAIK CS5 can export animations to HTML5.

Ah ic, something like this?

Code:

#################      ############
#               #      #          #
#          #### #      #  ####    #
#   #####       ########         ##
#                              ####
###################################

One could use floodfill to fill the rooms and then use the glowfilter. I assume the player's start position and portals are always inside so you could use them as starting points for the floodfill.

Code:

#################      ############
#               #      #          #
#          #### #      #  ####    #
#   #####       ########         ##
# *                            ####
###################################
->
#################      ############
#################      ############
#################      ############
###################################
###################################
###################################

I don't understand why a glow filter does not work. AFAIK the glowfilter just paints all opaque pixels with the glow color and expands them with a blur kernel. This is topolgy independent.

donut shaped? I don't really understand what this means. The GlowFilter should always work. Maybe you have to paint multiple layers. Can you make a sketch with paint or something to understand your level structure?

GlowFilter (knockout=false):

use the GlowFilter with knockout=true and high strength/low blur.

Classic controls are hardcore, almost inaccessable... But they are part of the fun when you have mastered them. http://www.clonk.de/ce.php?lng=en is the predecessor for free. Clonk was a major part of my childhood.

AFAIK Clonk is the mother of all 2D Minecraft-likes (direct character control in combination with landscaping, engineering and construction work).

Clonk has some nice underwater gameplay too:
http://www.youtube.com/watch?v=p83_ONA9qyw#t=84s

Sub Culture is a great underwater game. There are quite a few submarine games.

Thanks. The game is still in alpha. If I come up with a better name why not change it.

Well I think the name has been spread over the internet already. Changing it may severely harm its popularity. http://www.google.de/search?q="King+Arthur's+Gold"

@MM I love your game Soldat. Soldat is one of my favorite games of all time . I think "King Arthur's Gold" is a good name especially because the game has already a fanbase / is a brand. Do you want to rename it / are you unhappy with the name?

@WelcomeToAwesomeness