I played a format that stated you could put creatures down as long as you had enough mana to cover their cost, but you couldn't attack with a creature unless yo

I played a format that stated you could put creatures down as long as you had enough mana to cover their cost, but you couldn't attack with a creature unless you payed for their cost. You would have to pay their cost every time you attacked with them. This variant meant you would need to prioritize spells versus attacking. You wouldn't attack with all your creatures so you could save some mana for a counter spell.