Or should I aim for tablets and leave it at that?
I personally do not own a smartphone, I am a dedicated lover of flip-phones. So my only reference to size is my PC monitor and putting my fingers on the screen to see if things are reasonably touchable at such a small size.
Image below: 320 x 480 pixels:
[attachment=29403:ui.jpg]
You can see the image is rather busy a lot of things are going to happen beyond this static image which does not include the light show of effects from the combatant chaos.
Not all, but the majority of interactive elements are on the image. Everything on the yellow bar is represents the player's controls, so ideally one would hold their smartphone as if it were a Gameboy/DS.
All the squares and green rings are interactive, but I am uncertain if the player team and enemy elements are an eye strain. Ignore that part because this is a wireframe with the final probably more akin to what the game sites look like.
The max size of the stage is 1920 x 1080 pixels without black bars and more left and right space.
Game: Combollision (Combo + Collision)
Domain bought no website.
Originally wanted to call it Combostruction (Combo + Construction + Destruction). It was close but the elements involved favored collision and it rolls off the tongue better.