WARNING: THIS REVIEW CONTAINS SPOILERS.

So after about a week of just sitting down and playing Super Mario 3D Land, I finally beat the whole game. And by beat, I mean I 100% everything in it. This game is a very great game and to anyone with a 3DS, I recommend you buy it. The game plays as a combination of New Super Mario Bros (DS), Super Mario Bros 3 (NES), and Super Mario 64 (N64).

New Super Mario Bros:
The layout is set similar to New Super Mario Bros. You go from World to World, completing platforming levels to reach the flag at the end. You are allowed to go back to any World and any Level to replay them to find items or secrets that you may have missed on your first run through. A returning feature are the Star Coins. Like New Super Mario Bros, each level contains Star Coins for you to collect. Some levels in the game need a certain number of Star Coins to be unlocked and to proceed further through the game. Also like New Super Mario Bros, after a certain point, Luigi can be unlocked to play through the game as well.

Super Mario Bros 3:
The whole game seems to be a homage to Super Mario Bros 3. From music, to items, to enemies, to the Flying Airship and Koopalings. Playing 3D Land gives you a nostalgic feeling if you're a fan of the Super Mario Bros 3

Super Mario 64:
Now unlike previous Mario games involving getting from Point A to Point B involved you moving on a flat plane till the end, 3D Land expands that by giving you a 3D plane to play on. You travel in any direction to reach the end, and not just left and right. The game is linear, though there are different paths you can discover that leads to hidden secrets and items. Also new for a handheld Mario are the additions of cannons which the player can shoot off at in any direction...of course there is usually only one path the player can take so it would be silly to shoot off anywhere else.

Now just because the game uses a lot of stuff from previous Mario games, that doesn't mean it doesn't have a few new tricks in store to show off to fans. Some new items include new enemies to fight, a new power-up (Boomerang), the Mystery Box, and a whole new set of Worlds to play after the first 8 are completed.
The Mystery Box are purple boxes that appear in some Worlds that when accessed give Mario a 10 second task that ranges from coin collecting to enemy killing. If he completes his task, the Box drops a Star Coin (or 2) and some coins, making unlocking levels easier. Once accessed, the Box falls asleep for 24 hours but can be accessed again right after.
After completing the first 8 Worlds, a Warp pipe appears in each World leading to sub worlds called Special Worlds. The layout is exactly the same as the Worlds above, but with an added level of difficulty. Most of the levels are the same, but with different ways of completing them with new challenges and different Star Coin locations. While in the Special World, the Tanooki suit can be upgraded to the Metal Tanooki suit. Both suits function the same way, but with the Metal Suit, Ground Pounding turns Mario/Luigi into the Tanooki Statue featured in SMB3 with the same ability to make the player invulnerable while taking away their ability to move.
Unlike the Worlds above, each Special World has a level that needs to be unlocked with Star Coins while Special World 8 requires all the levels to be unlocked, making grabbing the Star Coins in each level something that should a necessity to beat the game.
And finally, if you beat each level in both Worlds and both Mario and Luigi, grab every flag at the very top of the pole (flag becomes gold), and collected every Star Coin in every World, the player is given a bonus level to play. I will not spoil how the level goes as I've spoiled enough, but doing all that and beating this Level is the only way to 100% the game. Nothing happens when you 100% it, but you just feel a sense of accomplishment.

A minor note: If you're very bad at the game and die too many times in a level, the game will reward you with one of two different power ups, the White Tanooki Suit or the P-Wing.
The White Tanooki suit functions just like the Regular Suit (not the Metal one) but with an added bonus of invincibility throughout the whole level. The suit changes to normal once the level is complete.
The P-Wing functions differently then the one in SMB3. Since flight is not obtainable in the game, the P-Wing just warps you to the end of the level.

These power ups are no longer available after you access the Special Worlds.

WARNING: The games runs off a Star Rating (5 stars unlock the Special Level that I explained above) and if you see any of the two special power ups (don't have to grab them), your stars won't produce a sparkle effect. It does not effect gameplay and you can still unlock the Special Level, but you just don't feel good inside.

Well that's my review, sorry if I ruined the game for you.