Thanks for playing and the feedback. We did want to add more VFX, especially an enemy explosion, but did not get around to it.
There should be a shield showing when you get it. At low levels it is a bit faint, so might have been lost in the background. As you level up it, it gets brighter until level 5, and shows its state by how faded it is.
We will take a look at the backgrounds, and see about adjusting them so the defaults are better. In the jam version the background is layered, and you can adjust which layers show in the settings. There is a setting for the clouds, and several for the stars/planets.