Well done art reflecting the sonar look. It had the right feel for the game. I did run into an issue on level 4 with my first play seeming to have an enemy outside the play area. I looked for a while, and then looped around the edge several times and could not find them. Restarting the level I was able to quickly locate them all. It also seemed to me like the mines all spawned together, or I could at least just keep shooting the same mine until it showed none were left.