Mario Adventure

Complete ROM hack of Super Mario Bros 3 created by DahrkDaiz, available here. Among the things changed from the original game:
 * The levels and World maps, completely new from the ground up (except for the occasional Nostalgia Level).
 * A central "hub" where all seven Worlds are freely accessible. The player will always resume their game here.
 * Several brand-new power-ups, along with a version of the "spare box" from Super Mario World.
 * An "improved" Fire Flower, which now gives Mario a higher jump and fireballs that go in a straight line.
 * Many of the graphics have been re-done or replaced, and the weather changes randomly every time you enter a level.
 * Infinite lives; coins are now used to buy items.
 * A functional "battery" save; the game can be properly played without using save states.
 * Getting to World 8 now requires a Key to be found in each of the first seven Worlds, with Princess Toadstool/Peach giving hints upon beating each World.
 * Warp Whistles now lead to a bonus area that is unique in each World.
 * Nintendo Hard difficulty, but also infinite lives and no Platform Hell design for the most part. Also, if you're really stuck, the Fire Flower or Wand power-ups will let you skip through most of the hard stuff.
 * And most importantly of all: Kuribo's Shoe is playable in every level, and can be tucked away in Hammerspace.

So basically everything except the music, the basic concepts, and Mario.

This game provides examples of:

 * Classic Cheat Code: Several, including one for a Sound Test.
 * Game Breaking Bug: If you're playing on NESticle, the "battery" save doesn't work. Not really that game-breaking, however, because you can easily work around it using savestates.
 * Hailfire Peaks: A few of the worlds. See Video Game Settings, below.
 * Invisible Monsters: Boos now turn invisible when you look at them (which still stops them in their tracks). Spot checks (by looking the other away once in a while) in fortresses is recommended.
 * Kaizo Trap: If you're fighting multiple Boom-Booms, it's a bad idea to pick up the mushroom they drop while there is still a Boom-Boom left, because you're vulnerable but motionless while the victory music plays. If you're not powered up and/or the surviving Boom-Booms aren't of the flying variety, you'll probably get killed.
 * Mini Boss: Get ready to see Boom-Boom waiting for you at the end of every normal level, except in Desert Dares.
 * Minigame Game: World 7, "Desert Dares". Each level is just one screen, with a catch — you either have to make a tricky jump, collect all the coins in time, or survive for a certain amount of time.
 * Self Imposed Challenge: Like the official games, try getting through with minimal use of the power suits.
 * The Spiny: A lot of enemies, such as the big Hammer Bros., have spikes added on. Fortunately, there are a few powerups that let you stomp on them still.
 * Video Game Settings
 * World 1 (Koopa Plains) is Green Hill Zone.
 * World 2 (Hotfoot Caverns) is a combination of Underground Level and Lethal Lava Land.
 * World 3 (Lakitu Glacier) is an exaggerated Slippy Slidey Ice World: every surface is slippery. Also, the weather effects can make it snow in any level, turning it slippery.
 * World 4 (Kuribo's Woods) is Lost Woods.
 * World 5 (Starry Slopes) is a Space Zone.
 * World 6 (Colossal Classics) is an interesting mix of Nostalgia Level and Macro Zone, as it's mostly giant versions of levels from older Mario games.
 * World 7 (Desert Dares) is ostensibly Shifting Sand Land, but see Minigame Game for what it really is.
 * World 8 (Bowser's Castle) has seven difficult levels, each in the style of one of the previous worlds before the final showdown.