Patch 1.0.6 - Minor bug fixes

Just another round of improvements: [list] [*] Computer cannon statistics now register correctly on the game's final stat screen. [*] The final stat screen now properly displays the computer's difficulty. [*] The game's targeting system will no longer attempt to automatically target a valid tile, but will instead display an error message. This was originally implemented to help the player, but it proved to be too disorienting. [/list]