Well, the Vita has a touch panel on the back that can be used instead of the front You could also use a point-and-click idea wherein you tap where you want the ball to go and it rolls there. Also, you could drag the ball by a rope or string that way you have room to see the ball and where it's going.

I suppose it could be hard to use (I'm not familiar with the responsiveness of the vita's touchscreen) but you could have a miniature display of the game in the corner which you would manipulate so your figure didn't cover the game.

To make up for the obstructed visual information, you could have a sound system that gets louder the closer your ball gets to anything. If the screen's cluttered though, it could get a bit chaotic.

You could also have a temporary time slow field around the ball to compensate for limited information so if you find yourself in a fix you could activate it. An area of effect bomb or temporary deflector shield would serve the same purpose.

You can also make a portion of the screen to be the ball control zone and control the ball as if you were using a touchpad. The touch-screen interface is not to blame here. Every interface has advantages and disadvantages. The game should be designed with those in mind from the ground up. Touch screens are pretty good when it comes to swiping so games like Infinity Blade that take advantage of this work best on tablets and smartphones, and if you were to port the game to the PC you would experience problems if you try to adapt it to using the mouse. For your game, if the platform you are developing it for is the IPhone or a similar device, and if you are using a top-down view, I would try to use the built-in gyroscope instead and adapt the gameplay to that.

Inspired by eugene2K and using some of Waterlimon's idea you could do a touch anywhere but my suggestions is a camera tilt system. The touch anywhere enables skilled players to deal with the limits of their control system on their own. The mechanic would orbit the camera as the ball rolls forward based on the touch and drag the player hits and would gradually intensifying the tilt and increasing the speed the longer the direction is held. Up would direct the ball forward (the natural direction to move), side to side would turn the ball while rolling forward (I would suggest turning the camera first then the ball) or strafe if the ball is not moving (top down view) and back would stop the ball from rolling forward and back it up if its stationary.

Swiping up could allow for the ball to automatically start rolling at full speed in a that direction and remove the hand from the screen for visibility but also increase risk since a second swipe or press and hold to maneuver would be required when dealing with a threat. The tilted camera would also give some extra time to react to the game threats. This creates a skill and risk system for players to consider when playing, making it clearer what they are learning to do but hard to master. I think it might give a more dynamic look to the game too. If you wanted to play more with the camera, have it gradually pull back the faster the ball rolls forward (not too quickly though otherwise you lose the sense of speed and you could add collisions on the threats so the camera has to move around threats, creating a natural screen shake as the player successfully passes threats at speed. Can I suggest ball deformation when reaching high speeds as well? When hitting down to stop the ball, some fun skid stop particles and ball deformation could be used.

Hope this is clear and applicable to your design.

Leveraging the ideas above -

how about to give the control feel of the inclined plane?
The idea is like your game device is glued on the bottom of a ball and by swiping on the left display's edge you make the top
of the ball roll up/down which would make your glued device inclined - and your boulder wants to reach the lowest position as
in the gravity field. (same mechanics for the right left direction)

It would be nice if higher slope of the plane would result in more acceleration of the boulder. Also the camera can orbit (simulating that
the plane with a boulder is inclined) for easier orientation but not necessarily. To make the game little more challeging the boulder
should have some momentum.


or the "derrick" option for the game?
At the center of the display there would be some crosshair indicating the position of the jaws. First task to transport the boulder would
be to aim over it, preferably using the left and bottom edges separating perpendicular directions (top/down, left/right). After the aim the
second touch and swipe down will be needed representing that the jaws unwinds down for the boulder. Then there would be a test if the
grip was succesfull based on accuracy of position of the jaws (or maybe other parameters, inducing the scenarios like using the special
jaws for the icy boulders).

So now assuming the boulder is succesfully graped the third touch and swipe on the left display's edge will be needed representing the
boulder is raised up from the terrain. The terrain should be 3D force you to estimate the required pull up for the transport. However the higher
is boulder raised the more difficult it will be to make it rocking/swinging (the derrick was sabotaged and cannot transport the boulder
by translation :-)). Rocking would be done by swiping the display 2D at the bottom part of display (higlighted by some indicator). The goal
would be reach the right oscialation (amplitude and direction) and combine it with the right timing of the swipe down on the left edge of the
display representing the bould is lowered down on the place...

The first game with inclined plane driving force would be flashy whereas the second one with the derrick would be slower paced but technical...


Good luck, and please let us know your solution...