Advanced format ruling
Wave-Motion Cannon
Card effect (current official text)During your Main Phase: You can send this face-up card to the GY; inflict 1000 damage to your opponent for each of your Standby Phases that have passed since this card was activated.
Current rulings for this card are maintained by Konami.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Advanced forum — sourced change requests get reviewed.