I really liked the duality of the space bar being horizontal and vertical movement based on timing, it worked really well. I'm not sure if it was a bug, but the music seemed to cutout whenever I fired, which felt a bit off, music cutting out is usually a sign of a mistake (such as missing a beat in rockband, or taking damage). The different orbs were clever. I think:
Green - Standard
Red - Out of range
Blue - Fully charged shot only
Pink - Follows you for a bit (I think this one followed you for just too short, I never shot it, and just had to damage boost through it).
Great game overall, I really like the idea, works well with the theme.