One of Nintendo's greatest games ever made.
The very first noticably different change in the conrol of Mario is the ability for him to do all kinds of flips and kicks, as well as punches that were not in the previous more technically restricted games (just climb a tree and see.) Taking a swim is probably the funnest thing to do at the start, although like any homosapien Mario needs air and he will drown fairly quickly in the early stages in the game.
While starting off is quite easy, you just run up to your enemies and throw or jump on them to defeat them. As easy as defeating your enemies is if you progress through the game too fast you will find yourself stuck and wondering what or how to do what is required. Reading the sign-posts will help along the way, so if you decide to finish every level completely (collecting every star) you'll be more aware with the game as it progresses into more deeply challenging levels and situations. Situations being the fights with Bowser, and the little mini-quests you encounter if you want to collect every star to complete the game.
The Nintendo 64 is one of the best consoles ever, with some of the best games ever made, this being one of them, no gamer young or old should miss out on this truly original and classic game.