This game is rated E (for everyone).
When I bought my first Nintendo game many... many years ago, I loved being able to control Mario, jumping him from pipe to pipe and over the razorblades. I developed many techniques to get Mario to the end of each stage, but I was always intimidated by Bowser. So when I found this game that was 2D with special 3D features, I was so happy. It was like I was back into the fun days of video gaming.
This game has a story of Princess Peach being kidnapped, but not by Bowser. And, Bowser is your ally. You are trying to save dimensional worlds from being sucked into a black void. There is a second story of love lost and found. You are still dealing with koopa and other bad guys, but if one of the puzzles are impossible or very difficult, then switch to 3D. The path clears or at least you see the obstacles better.
You did not have that option with the first Mario Brothers game.
During the late fall, I fell into a hole (really... these things do happen to real people) and hurt my knee and leg. I spent about three weeks or so on my back playing this game. It game me some time to heal with my brain racing with Mario. Also, I suggest that you get the hint book. I could work out the puzzles eventually, but it was much easier in the harder levels to have that Nintendo sanctioned book.
So have fun... and enjoy. It was fun and relaxing.