Like the title, a variable light source that can ramp up and down its brightness. Maybe something like the creative light block that comes in different strengths and durations or a way to set them with a GUI.

Thanks for your idea!

What about Redstone, maybe light level controlled by Redstone level?

That would be cool also.

Take a look at this video and time stamp, and see how the crystal pulses like a heart. I just thought it would be cool to have a light block that did something like that. https://youtu.be/a5CedG_bf80?t=872