There seems to be something causing lag spikes to occur every once in a while. It occurs even when no towers or enemies present. Frame rate drops from roughly 60 FPS to as low as 20 or 30 for a few seconds at a time.

Seems to be related somehow to the more zoomed-in map sizes. Haven't noticed this problem on the larger map sizes. So far observed on maps with tile size of at least 36px. Always seems to occur once enemies have already spawned on the map.

Intermittent significant drops in frame rate seem to occur when enemies are moving

Framerate stays at around an average of 30 fps consistently, even when no enemies are active, dropping as low as below 20 fps at times.

If you have a tower tapped on than restart you can then sell the tower making it unfair at the start

The method of calculating distance to the exit currently does not account for the fact that enemies may not take the shortest route due to path tiles forcing them to take a longer way. Because of this, if there are crossovers, towers seem to target the enemy physically closest to the exit rather than the one furthest along on its path.