NOTE: This may go hand-in-hand with another improvement I've kicked around adding -- a "casting" spark/threshold over the main bar that fills from right->left for builders/left->right for spenders and shows the progress of your current cast.

Fill the Holy Power bars that will be generated when hardcasting an ability.

Some notes to future Twintop, specifically about Holy Paladin:

Infusion of Light procs cause Holy Light to give 2 Holy Power.

Tower of Radiance should give 1 Holy Power always when you cast Holy Light.

With an Infusion of Light proc (+ Tower of Radiance talented), you get 3 Holy Power when you cast Holy Light.

Additionally, when you have an Infusion of Light proc (with Inflorescence of the Sunwell), it has an independent counter that, after 3 IoL casts, will give another 1 Holy Power. This gives 4 Holy Power when it happens.