Messed around with making some simple graphics.
Messed around with particle effects.
More particles!
Added a simple memory logger, basically a memory version of libgdx's FPSLogger.
Separated the draw and removal loops for the particle effects array.

Removing particle effects during the loop lead to some effects being skipped for that loop, i.e. they wouldn't get updated or drawn and would appear to flicker.
Little bit of tidying and refactoring.
Added a scoring system.
Enemy hitting the player now stops the game.
Added another enemy type that simply moves across the world at a constant velocity.

A second enemy type also meant changes in some of the systems to select enemies rather than just entities with the AIMovementComponent.