I love the borders, but there's way too much wasted space around the play field. I suggest making the play field bigger, as it is currently a tad bit small.
Actually, the borders with the footsteps are going to be a crucial part of the game. The thief player will be hidden to all players except for a brief moment at the beginning of a match. The red footsteps tell the players if the thief has moved. The players playing the Cops can use that info to judge how far the thief has moved, although not which direction. The thief player can use the footsteps to help gauge where he is. E.G. if he taps up but no footsteps appear, he has hit a wall. It's a little more intuitive once you see it in action.
Also, i think i will need to keep the playing field the size it is because if you are the thief, it will be more difficult to track yourself on a larger playing field.
I think i will be able to put up a build pretty soon. I'm curious as to people's impressions and totally open to suggestions of gameplay mechanics. I realize that most people prefer online games to hotseat, but i hope to make this worth getting a few friends together.