The Mega Man Zero series is a spin-off of a spin-off, but you wouldn't know it from the highly polished gameplay and presentation these games bring with every new entry. The fourth game retains all the great, tight action you'd expect from any Mega Man title, and it also does a nice job of streamlining the weapon and Cyber Elf systems that have been so complicated in Zero's previous adventures. The result still looks and plays a lot like the first three games, but that doesn't stop it from being one of the best action platformers on Game Boy Advance.

Zero has always been known for his green energy saber, which makes playing as him more visceral than Mega Man's buster-based tactics. Zero still has his own buster gun, though, and it is useful at times. All the other sub-weapons from the Zero series have been thrown out in MMZ4 in favor of the Zero Knuckle, which lets you temporarily steal weapons from enemies for a huge new variety of attacks without complex ammo management. Most of the stolen weapons are not as useful as your basic sword and gun, but a few of them can give you an edge over a difficult mini-boss or a nasty platforming section. The Zero Knuckle also lets you hang from rails, and it's occasionally used for environmental interaction like yanking out cords or pulling switches.

Speaking of environments, the story in MMZ4 involves a plot by Dr. Weil (who looks like a cross between Dr. Wily and Batman's Mr. Freeze) to destroy what's left of Earth's natural environment, forcing human refugees to return to Neo Arcadia, the human sanctuary held under his diabolical rule. The drama is heavily anime-inspired and predictably takes itself too seriously, but this is probably the most comprehensible plot in the Zero series. All eight main stages tie in somehow to the plot against Earth's fragile ecosystem, and in fact, you can set the weather pattern before starting a level. It's supposed to open up new paths and make certain enemies easier or harder, which is a cool idea, but the effects are not pronounced enough to make most levels worth playing through twice just to check out the alternative forecast.

The biggest improvement in MMZ4 is that the special moves and bonus items are generally easier to find and use without severe penalty to your score. The game is still incredibly difficult at first, when you have nothing but your basic weapons, but you can expect to acquire a great many useful add-ons by the end of the game. The Cyber Elf system has been idiot-proofed so that all you need to collect are energy crystals to level up the single elf, which can power up Zero with all kinds of useful abilities, three at a time. EX Skills (Zero's cool saber and gun special moves) are automatically unlocked if you defeat a boss under adverse weather conditions, so you no longer have to play a stage perfectly to gain them. Even more abilities and stat boosts are activated by chips, which are built from spare parts dropped by enemies. The game's characters are stingy with chip recipes, but you can easily find a complete cookbook online to make Zero double jump, run faster, reflect enemy shots, and more. Even the can't-live-without Sub Tanks are pretty easy to find this time around.

One of my biggest complaints with MMZ4, and the series as a whole, is that you can replay levels but never get a better score than the first time you beat it. This issue isn't nearly as important as in past games, since you don't really need to get A or S ranks to unlock abilities, but it still sucks for those of us who like to earn good scores without having to constantly reset back to an earlier save file. There is, however, an awesome New Game Plus feature that lets you play through the game a second time with all your chips, EX Skills, and Cyber Elf levels, so you'll have a much better chance of getting those impressive ranks at the end of each level.

If you've played some of the earlier Zero games, you may be looking for more innovation than MMZ4 offers. To be perfectly clear, the core gameplay has not changed at all since this series debuted on GBA…in fact, it hasn't changed at all since the original Mega Man. These games are differentiated by a series of small improvements and changes that sometimes result in significant, if superficial, changes to how you play. More than in any other game in the Zero series, MMZ4's changes work together to make the experience smoother, less frustrating, and more empowering to the player. If you haven't yet burned out on Zero, you're going to love the tweaks. If you're new to the series, you'll be spared from many annoyances that plagued the earlier titles.

Zero's newest game is just as short as the others (it took me about five hours my first time through), but there is the aforementioned replay mode, plus a couple of harder difficulties to unlock, and even some weird mini-games that open up when you beat the main game. It ends up being at least as big as most GBA action games, but Mega Man Zero 4 is of much higher quality than most of those others. It looks incredible, sounds great, and plays beautifully…what's not to love? If you haven't yet tried out this excellent series, this is the best game to start on.