I perfer lights' indirect way of control, then darkness' manipulation for this card.
If it was time, it would interfere with sundial. If it was darkness, it would interfere with cloak. Becuase it's light, there is no problem.
By creature effects, this would mean you can't use the ability again I assume? And graveyard would still bring only one to the field? Acceleration would give an additional +2/-1
One thing I don't like is that it's too situational. It only it had something more but simple like gaining 10HP
Yes, I mean creatures' abilities will not be reusable even after playing Sundown/Sunset. That includes "passive" active abilities, such as Bioluminescence and Acceleration. However, I don't get what you mean in reference to Graveyard. There isn't really any turn-based mechanic related to it.
As for the healing, I don't think so, since Light already has so much healing.
Fast Forward
idea taken.
I'm sorry, I seen that. I'll be more cautious about repetition and redundancy in later submissions.
In my defense, if it means anything, there are some subtle differences, albeit small.