If there's one series I've liked playing through the years... okay, that would actually be the Gradius series, but if there's a second series I've liked playing, it's Mega Man. The franchise has had many great games over the last couple decades, but since Mega Man 10, the classic games have kind of... well, stopped.
Or at least, officially there hasn't been a new classic game since 10.
There have, however, been a few fan-made games to pick up the slack. One such game, Mega Man 4 Minus Infinity (or Rock Man 4 Minus Infinity/RM4MI), is a game that truly deserves any Mega Man fan's attention.
In development since 2008 (yep, around the time Mega Man 9 was released) and finally reaching version 1.0 in December 2014, Mega Man 4 Minus Infinity is pretty much a completely redone version of Mega Man 4. Specifically, it uses the Japanese version of the game, hence the title screen saying Rock Man instead of Mega Man. What makes this especially interesting compared to other fan-made games is 2 things: first, it's not a PC game, but a hack of an NES game, so it could be played on an actual NES (in fact, there's a site that sells reproduction carts of the game). Second, unlike some other ROM hacks out there, this game feels a lot like it could be an an actual Mega Man game, though a rather tough one.
The story and gameplay for Minus Infinity is... well, pretty much the same as the original Mega Man 4. 8 robot masters need to be defeated, and there's a fortress or 2 to be stormed. If you've ever played a Mega Man game before, you already have a good idea what to do.
Now for what makes this game so different from Mega Man 4... as I said before, Minus Infinity is a completely redone version of Mega Man 4. By completely redone, I mean 99% of the game was changed. Stages, stage music, boss patterns & attacks, enemies... the only real similarities between this game and the original are the opening sequence and the story. Even the weakness order for the robot masters was changed, so veterans of the original game will still have some trial and error to go through on which stage to pick next.
The most obvious change you might notice in the game is the music. All the songs in the game are NES-style versions of other game music. For example, the Silence music from F-Zero X is used for Bright Man's stage, and the Pokémon evolution jingle chimes when a boss is defeated. The music choices seem odd at first (Princess Tomato in the Salad Kingdom? Really?), but they still work.
Another interesting change is how Rush works. There's no Rush Coil in this game, and Rush Jet & Rush Marine are used only in fixed spots. There are, however, replacements. Rush Search from Mega Man 7 can be used, and 2 new weapons are obtainable, including a cannon that kills anything in one hit. The Wire & Balloon are still here, though with different uses, and Beat and Eddie also make appearances.
The rest of the changes mainly revolve around difficulty. Invincibility lasts much less than the original game, so it's not quite so easy to just run through areas. Bosses also have longer invincibility from your buster to encourage using robot master weapons. Damage taken appears to be greater, though I can't say 100% there. Basically, it's a bit tougher than the original game.
If you don't like the difficulty, a major feature was added in the 1.0 version of the game: customizable difficulty. You can increase or decrease invincibility time, damage taken, how often items drop (of if they drop at all), and even how many lives, E Tanks, or HP you start with. You can make the game as easy or tough as you like.
For replay value, the game has a scoring system based on how well you play and what secrets you can find. There's also an Arena mode similar to Kirby Super Star's arena, a time attack mode, and 4 achievements you can attempt to get. These extras can provide a great challenge for those willing to attempt them.
It's tough to truly describe how good of a game Mega Man 4 Minus Infinity is. It's a game that should be experienced in whatever way possible for all Mega Man fans out there. We may never get a Mega Man 11, but this game might make up for it just fine.