Synopsis for people who've never played Megaman series before: This game, as with all games in the series, is a game where you basically play as robots fighting a war against other robots for the sake of humanity. It is a side-scrolling action game that involves a lot of running, jumping, shooting, climbing, bouncing off of walls, and memorizing AI patterns to beat enemies. This game has a system built into it where each boss you beat gives you a weapon you can use to beat another boss somewhere else. Stages are full annoying enemies and one-hit-kill gimmicks designed to make your head explode. The game's playable characters are two robots called X and Zero who can gain upgrades and become more powerful as the game goes along (these are usually well hidden).  It is an 'anime-style' game made by Japanese publisher Capcom (authors of Street Fighter amongst other series).

Megaman X3 - Zero Project is a hack of the original game for the SNES: MMX3. What this hack adds is a fully playable Zero and a lot of extras as well (new cutscenes, new abilities for Zero, new and different gameplay, and at least one new secret).

In the original Megaman X3, Zero as a character was only partially playable. He could be summoned into any level, play only 1/3rd of it, then gets forced to leave when he approaches a boss door. He could not play any more than a 1/3rd of any level, he could not gain new abilities, and he could not use upgrades. Also, if he died he could never be used again. He had only ONE life. For Zero's very first playable appearance... it absolutely /sucked/. Zero was useless except to kill him off in Doppler's 3rd stage so X could get his saber... which killed any boss in two hits.

Megaman X3 was a great game, but for the above screwups on Capcom's part it really had a lot of untapped potential.

This hack changes all of that: Zero is now fully playable throughout the entire game and X is not necessary except for a few small parts. Zero can also: 1. Gain boss moves and use them, 2. Get upgrades and use them (Heart Tank, Sub Tank, Ride Armor, Xs parts also give Zero enhancements), 3. Gets a secret upgrade which I won't spoil but it is very cool!.

Playing as Zero does, however, change game dynamics quite a bit. This game is notorious for being one of the hardest in the X series, but playing with Zero can make some fights tremendously easier. In fact, Zero is so powerful that he does not have to exploit Boss weaknesses. Landing all three hits from his fully charged Buster does considerable damage to almost every boss. There are two mini-bosses that can die from a /single/ Z saber slash. Zero also starts the game with more than twice Xs healthbar which makes him a great choice for fighting bosses before X gets his parts.

THAT SAID.... X is not left in Zero's proverbial dust here either. By the time X and Zero get all of their upgrades, X is a very good alternative to Zero. He is less powerful than Zero overall but he can tank hits far better, is small and harder to hit, faster and more agile, his shots cover more area, AND he can heal himself outside of boss rooms and fill up subtanks just by standing still. He can also STILL get Zero's saber if you choose to kill Zero off.

Also, playing as either X or Zero gets you different in-game cutscenes for some fights which makes this game worth at least two playthroughs. That, and, there are divergent paths through the game which lead to different boss fights and the only way to see all of these divergent paths is to play the game more than once.

One thing I will say about this game's difficulty though... and this applies especially to the original where Zero is not truly playable... even with Zero being the warmachine he is... some of the boss fights in this game will have you tearing your hair out. Do not play this game if you have a weak heart or blood pressure problems!