Phew... Gonna reply now...
I just tried it, really well done, runs smoothly on my computer, and sounds like fun !
My only advice, if you want people to play your game, would be to avoid making a Terraria clone for the simple reason that is... it already exits ! (or maybe you want to build a free clone,

)
But I 'm sure your game can become awesome. Keep on with your great work !

Same as
Although your game may look like Terraria now, you could still make it different from Terraria, as Jimmt said. Unless of course, you don't want to.

Just please don't make the same mistake Terraria made, which was that once you beat the game, you don't feel like playing anymore unless there's some major update. After basically doing everything possible, me and the friends of whom I was playing Terraria with quickly got bored. Keep this in mind when designing the actual gameplay of WorldOfCubes.

Other than that, it's looking really great so far! Keep developing for this, it seems like you have lots of potential for a fun game here!

Not thought about really "selling" it... Also, yes, of course it looks like terraria right now. The beginning is always the same: You can mine blocks (thats just like Terraria, Minecraft, All other Minecraft 2D's and Infiniminer, Blockworld, and many more games).
The following steps make such kind of games different.
Terraria: You mainly get Armor, weapons and fight with bosses.
Minecraft: You build awesome ... Things... It can be anything.
Now, what is planned for WorldOfCube is tricky to say.
It's planned to add some kind of evolusion. You kind of start with a little tree, a little house, some mining and so on. Now, to make your life awesome, you begin to build awesome machines with ... anything.
You will have a level up system with both mining skills, and weapon skills, maybe even "electronics" skills.
But back to the presence:
TODO-List:
- Better, Graphical Patcher
- Working Inventory, making you need to get resources, etc
- Mining system
- only mine in a specific radius, make the player look in the direction you mine with the right mouse button too, right now only left works
- make you need time to mine blocks.
- add an Item bone to the player, to be able to carry, blocks graphically
- add kind of a .... erm... thing, which shows you, if you are editing in foreground or background, (currently possible to switch with "F" key. (to see command-line output, start in bash/cmd with "java -Djava.library.path=lib/native -jar WorldOfCube.jar"))
- Limit gameplay and hacky things, like not being able to die.
- Things which are mentioned above, and will appear much later.
- Oh, I forgot the Crafitng system... have to think about that too... maybe you have some Ideas?

Special Quote:
Just please don't make the same mistake Terraria made, which was that once you beat the game, you don't feel like playing anymore unless there's some major update. After basically doing everything possible, me and the friends of whom I was playing Terraria with quickly got bored. Keep this in mind when designing the actual gameplay of WorldOfCubes.

Oh man! Thats the point. It was the point through all the time, developing this game. Yes! you will be able to get much more intresting things to see, with the planet-system. You will be able to get on other planets. It's something, I have to work on later, which will take a lot of time, and keep in mind, planets was the thing I always had in mind, when programming this game. Just take a look at my Blog, the first planet being generated is already SOME time ago...
Lastly, I REALLY love you guys, appreciating my topic

That keeps me on developing this game!
(Also, I'm so cracy about the Patcher, working on windows without having it tested... I wrote the Patcher completly "Blind" (!), I love Java

)