Players play with the top card of their libraries revealed.
The top card of your library isn't in your hand, so you can't suspend it, cycle it, discard it, or activate any of its activated abilities.
If the top card of your library changes while you're casting a spell, playing a land, or activating an ability, the new top card won't be revealed until you finish doing so.
When playing with the top card of your library revealed, if an effect tells you to draw several cards, reveal each one before you draw it.
This has the supertype world. When a world permanent enters, any world permanents that were already on the battlefield are put into their owners' graveyards. This is a state-based action called the "world rule." The new world permanent stays on the battlefield. If two world permanents enter at the same time, they're both put into their owners' graveyards.
