At the moment, changing the screen size will do that; on my mobile branch I addressed that issue and should back-port the fix sometime after voting is over. The idea is to lead the ant by dragging immediately in front of it, like a real ant's pheromone sniffer; it is an acquired skill and most of the game's difficulty though.
I'm glad you like the art, music, and atmosphere! I spent quite a while on that.
Thanks for playing!