If you use “Star Blast” on a monster in your hand and then Set that monster, its Level is still reduced and will be reduced when it is flipped face-up.
You cannot use “Star Blast” on a face-down monster you control on the field.
If a monster affected by “Star Blast” is face-up on the field, and is then flipped face-down (with “Book of Moon”, etc.) then the effect of “Star Blast” is wiped and the monster’s Level returns to normal.
If you activate “Star Blast” but have no monsters to use it on when its effect resolves, your opponent can look at your hand to confirm that you have no monsters in your hand.
You cannot reduce a monster’s Level below 1 and you cannot over-pay for “Star Blast”. You cannot select a Level 1 monster for “Star Blast”. If you paid 1000 Life Points, you cannot select a Level 2 monster, etc. If you had an appropriate monster to use “Star Blast” on, paid the Life Points, but no longer have an appropriate monster when “Star Blast” resolves, its effect disappears.
The maximum Life Points you can pay for “Star Blast” is based on the maximum Level of legal choices you have available at the time. You cannot over-pay.
If “Majestic Mech – Ohka” has its Level reduced to 4 or lower with “Star Blast”, and it is Summoned without Tribute because it is now a Level 4 or lower monster, its effect to send itself to the Graveyard does not activate.
Paying Life Points in multiples of 500 is a cost to activate this card.
This effect does not target. At resolution, you select the monster in the Hand/on the Field whose Level will be reduced.
If "Star Blast" affects a monster in your Hand, the monster's Level remains reduced after it is Summoned.
You cannot pay Life Points to reduce a monster's Level to 0 or below.
Example: If your only monster is a Level 6 monster, you can pay at most 2500 Life Points. You cannot pay 3000+.
Example: If you pay 500 Life Points, you cannot reduce the Level of a Level 1 monster.
Example: If you pay 1000 Life Points, you cannot reduce the Level of a Level 2 or less monster.
If "Spell Economics" is active, "Star Blast" cannot be activated without paying Life Points, since the effect depends on the Life Points paid.
If an effect is chained to "Star Blast" so that you have no monster in your Hand/Field whose Level you can reduce, your opponent can check your Hand to verify that you have no such monster.