Enclosed Ecosystem

Landfall - Whenever a land enters the battlefield under you control, you may pay {u} or {g}. If you paid {u}, create a 1/1 blue fish creature token called tadpole that has: {t}: Destroy target green permanent with less power than this creature's toughness. If you paid {g}, create a 0/1 green plant creature token called weed that has: Landfall - Whenever a land enters the battlefield under you control, you gain 1 life.
{g}{g/u}{x}{t}: You may play up to X more land cards this turn.