Once a fly is eaten, it should be replaced, ensuring that there are neither too many nor too few correct flies and resorting several flies if necessary (to avoid giving away obvious answers).

Once a fly has been built as either a valid or invalid choice, it should add an answer to its text based on the current question

Since a typical phone/computer screen will have more horizontal space than vertical space, it makes sense to have non-square grids to maximize space usage.

From a technical standpoint should be virtually no work. Just add a menu selection and swap which images are used in the game. Art-wise, the original character image can probably be used as a baseline, but the shape and color should probably be altered moderately.

Player, enemy, flies, etc. should scale on box_size, which itself is based on the minimum of width or height. This should make things look better at extreme resolutions

Right now level changes are very abrupt and somewhat meaningless. This experience could be improved by adding a separate level advancement screen and possibly speeding up some aspects of gameplay on level advancement.

Add a simple defeat sprite and sound when the user fails, to make the defeat clearer. Also consider adding information about the reason for failure (time ran out, enemy attack, incorrect selection etc.).

Might be tricky since love 2d doesn't support video playback. Would require coding whatever animations took place.

If a player has a destination as they are defeated by an enemy, right now they will continue on to that destination despite being defeated and inactive, which doesn't make much sense. Add some check in player's update method to prevent this.

Steps to page through describing rules/gameplay. Pictures would probably be helpful

When a box is near the edge of the screen, it might not display fully. I assume this is because the substantial line width causes the line to begin being drawn before the actual x/y positions. Could be fixed by adding an offset equal to that added by line width, though the box size would also need to be reduced accordingly.

Save high scores, view high scores, etc. Probably use love.filesystem.read, love.filesystem.write, and http://lua-users.org/wiki/TableSerialization. The file wouldn't be secure from editing but given the audience that's probably not an issue :)

^

Two sounds can be playing at the same time. For certain combinations (e.g. danger sound and victory sound), this sounds pretty bad. Look into a way to check if some sound is already playing perhaps? Else track duration of sounds to know if a sound is being played.

^^. Should also help with the move/eat sounds overlapping in a bad way.

Freezes game, with options to resume or quit to menu

Because screen sizes could vary considerably, it would be best to eventually use relative sizes for all drawings in the game.

^^^

Add enemies that move around the board and can damage the player

Lose life on each mistake.
Lose life when monsters hit player
Gain after x points?
When all lives gone, game over (go to menu)

Selectable from menu/pause, probably use love.event.quit() if that works on the android port. If there's a way to read the back button and let that quit it would also be good.