Fate of Io's interface is similar to that of a typical real-time strategy game. The camera is generally positioned to give a 3/4 overhead view of the characters and their surroundings. Along one edge of the screen, information about each current party member will be displayed, including a picture of the character's face and stats such as the character's current energy level.
Most commands are issued via the mouse. For the sake of intuitiveness, the controls are designed to emulate popular computer GUIs. The left mouse button may be used to select characters in order to issue commands to them. To select multiple characters at once, the player may drag a box around them, or hold shift or ctrl while selecting individuals. Additionally, the player may click on a character's portrait on the sidebar to select a character if this is more convenient.
With one or more characters selected, the player my issue commands to the character by clicking on other objects. Right-clicking anywhere on the screen will bring up a menu listing all of the actions which the selected character(s) can take relative to the object under the cursor. For example, right-clicking on the ground will usually show only the "move here" command. Right clicking on an enemy might show commands like "attack" or "taunt". Right clicking on another character (or that character's portrait) might show commands like "heal" (and also "select this character").
Left-clicking somewhere orders the character(s) to perform the default action on an object. This is a shortcut for whatever action is most common. For example, left-clicking on the ground automatically orders the character(s) to move to that location, while left-clicking on an enemy orders them to attack. As a visual aid, the mouse cursor will always show an icon indicating what the default command will be if the player clicks.
At any time, the player may pause the game by pressing the space bar. While the game is paused, the player may select characters and issue commands to be carried out once the game is resumed. This allows the player to use complex strategies and tactics without having to have incredibly fast reactions.
How should the camera operate? It probably should not be possible for the player to view areas that the characters haven't seen yet, or to see moving objects in areas the characters can't see. However, a camera fixed on a character would be limiting, and "fog of war" is perhaps overused.
How should we highlight "special" objects which can be manipulated? I don't like games where the player is forced to wave the mouse over the screen (or worse, click everywhere) looking for special objects, but they should be highlighted in a way that doesn't ruin the graphics. Perhaps they should be outlined when the player holds ctrl or something along those lines.