After three enjoyable Mega Man Zero entries, Capcom just had to sneak in one more. Released extremely late into the Game Boy Advance's life - after the Nintendo DS had already been released, in fact - Mega Man Zero 4 is the final game in the series and mostly follows along with the previous three titles.
Once again picking up where the previous title left off, the game opens with Zero saving a group of humans from a new bunch of enemies, called the Variant. He quickly gets taken to their base, a traveling caravan, and soon enough encounters another group of eight villains which he must then defeat one by one - the Einherjar Eight Warriors - and their leader, Craft.
The caravan will act as your base in this game, replacing the Resistance base from the previous releases. It's quite a bit smaller and has less rooms, making it much less of a hassle to get around. Otherwise, though, it serves mostly the same purpose as the old base.
It's pretty familiar after this point - pick a stage, beat the boss, and repeat until the final set of stages unlocks. Just like before though, there are some small gameplay differences to mix things up a little. For starters, Zero once again starts with the Z-Saber and Buster Shot, but does not have a rod weapon as third option. This time it's the Z-Knuckle, which allows you to do a variety of things like punching enemies, hanging from certain objects, destroying certain blocks or even stealing enemy weapons for your own use.
Also new is a weather system, which allows you to pick what weather each stage you visit will have. Depending on the weather you choose the stage might be harder, but this will also allow you to acquire items or take routes not available with another option.
Many people thought the previous Zero games were quite difficult, so another newly included feature is an easy difficulty mode. This can be useful to get the hang of things, but you will most likely eventually want to try the regular difficulty instead, as the aforementioned weather system and most unlocks are not available or attainable in this mode, essentially locking you out of many of the game's features.
Customization played a large part in the previous games as well, so naturally it returns, but not without some alterations. Cyber Elves no longer need to be collected - instead, you will get a single Cyber Elf almost immediately. This one can be levelled up to learn additional skills, of which only a limited amount can be active at any time. The secret disks granting Zero powerups have also been removed, instead being replaced by parts dropped by enemies; these can be used to create items, though unfortunately most of the working combinations can only be randomly guessed and will not be revealed through any other means.
Finally, again like before, you're also able to unlock a variety of unique minigames if you beat the game under certain conditions. They're a little more straightforward this time, but that doesn't make them any easier!
Being one of the last high profile GBA games ever made, Mega Man Zero 4 is quite excellent on the technical side, with terrific sprite-work and a rocking soundtrack that really gets the most out of the system's sound chip.
At this point you should know what to expect from the Zero games - Zero 4 delivers more of the same excellent gameplay, though those who like their games tough might find it a bit of a shame that it's been made even easier after the already simplified Zero 3. Thankfully, the easy mode is completely optional, and there is still a secret hard mode if you want a truly harrowing experience, as well a plethora of unlocks that are quite difficult to acquire.