Astro Boy just might have invented a new game genre.  It comes into the world with a complex (but easy to execute) blend of evasive flight moves.  The indication is that Astro Boy has the power to fly, but in the game you're limited to dashing and hovering only.  This creates the challenge that hardcore gamers will welcome and endure, and is the reason why Metal Slug fans will be eager to get their hands on it and unleash their hard-earned skills.

Despite having levels and enemy situations that are nearly as difficult as Metal Slug, the gameplay experience is much different.  There's shooting in this game, but it's not the primary form of combat.  Astro Boy is loaded with a Dragon Ball Z-style laser beam; a powerful, combo-creating kick; and three special attacks that deal optimal damage.  He can punch his enemies several times for multiple consecutive hits, but it's the kick, which can only hit once, that's really fun to use.  Most enemies will be thrown back, hitting anything in its path.  Should the kicked enemy have four baddies behind him, they'll get knocked around like bowling balls.  This move is heightened with great sound effects -- successive beats that get higher and higher.  Not drum beats, but the classic, 16-bit style beats you remember from the early 90s.

The dashing and hovering that I spoke of is perhaps the most important part of this game.  Astro Boy is at the mercy of his over-sized enemies, many of which have stronger attack power and a larger life meter.  Your only line of defense: dashing.  At any point in the game the player can tap the directional pad twice (left or right) to evade an attack.  You can also dash upward, and then choose to dash left or right before falling.  That sounds logical, but there's a twist: evading makes Astro Boy invulnerable to attacks.  He cannot be hit, touched or tackled at any time while dashing.  "Eureka!  This game will be no match for mere!"  That's what you think.  Astro Boy gave you this life-saving tool for a reason.  Knowing that you have hope, the developers decided to crush that hope by throwing in more enemies.  In some levels boss battles occur one after the other.  The game usually saves after each battle, making the challenge considerably less overwhelming than Metal Slug.  You still won't beat it in a day, however.  Maybe two or three days, but only if you're really hardcore.

With a taste of Capcom fighting games baked in the middle, Astro Boy lets players fill an EX gauge and execute one of three special attacks.  The EX gauge fills just by successfully hitting an opponent.  The attacks range from cool to extremely weird: a lunging fist; a powerful laser beam shot from the hands (this one is far superior to your standard laser); or a cannon that shoots from Astro Boy's shorts.  It looks weird and makes absolutely no sense, but that's true of everything in this game.

Astro Boy takes a cue from Devil May Cry by giving the player the chance to upgrade his statistics.  Life (energy bar), Punch (melee attack power), Laser, Shot, Jet (the number of times you can jet), and Sensor can be upgraded as you encounter Tezuka characters.  What's a Tezuka character, you ask?  I know it has something to do with the game's story and likely came from the cartoon.  The dialogue didn't hold my interest long enough for me to find out, but it didn't affect the gameplay.  It's doubtful that you'll require a more detailed explanation, but if you do the game manual should be able to help you out.

Given the game's heritage (and the childish hero on the box), you might imagine that Astro Boy has a a dark side.  Not a cool dark side like Anakin Skywalker, or a mature dark side that would prevent kids from playing it.

We Americans love great games just as much as Japanese gamers, so the gameplay can be equally appreciated in all parts of the world.  Their taste in television, however, is very different from ours.  Astro Boy's dorky looks, silly enemies and annoying story sequences will turn off most adult gamers.  As much as I enjoy playing this game, there were times when I had to take a break.  Even I – a hardcore gamer with varied tastes – can only take so much. 

Can't take these annoyances?  Then Astro Boy: Omega Factor should not be in your Game Boy Advance collection.  Otherwise there aren't any reasons for me not to recommend it.  Astro Boy is great the first time through and has that wonderful 16-bit quality that'll make you want to play it several years from now.

Gameplay: 9
If you want something different, Sega's here to provide it.  Astro Boy is one of the most unique titles you'll find on any console.  The new gameplay elements prove that you can still create innovation on old technology.

As Astro Boy, players find themselves in a world where enemies are sized like clothing, coming in small, medium, and large.  Boss battles are immensely challenging (some taking place one after the other!).

Not all of the levels are perfectly designed, but overall the gameplay is polished and worth coming back to.  Buy it for this reason and this reason only.  Just beware of the annoyances before you do.

Graphics: 6
Bright pretty colors, but we've seen it all before.  It's worthy of a 7, but I'm giving it a 6 because I can't stand the way the characters look (silly and childish).  The enlarged enemies are pixelated, giving me another reason to mark down the graphics.

Sound: 6.9
Adding to the graphical annoyances is the sound.  I love the combo sound effects (where one enemy bounces into another), but for the most part the sound and music lack any memorable qualities.

Difficulty: Hard
It will crush you.  It will stomp on you, laugh at you.  It might even point and stare!

Concept: 8
From a gameplay standpoint, Astro Boy is pretty awesome.  I love the idea of flying in a game, and even though you can't do that here, the dash/hover mechanics (which simulate flying) are really good.

Overall: 8.5
Astro Boy will surprise you with its challenge, its endurance, and its clever (and crazy) boss battles.  The dash-to-survive gameplay is very unique.  Never before have I been able to become invincible in a game so easily, yet still manage to die by the hands of my enemies.

Puzzles are nowhere to be found, but you could argue that the boss battles are like puzzles.  Their weak spot is rarely obvious, and even when you figure it out, it's not easy to get to it.  You'll have to do more than evade attacks to get through these tough baddies.  They'll suck you in, chew you up and spit you out.  Come to think of it, that's one comedic, over-the-top element this game didn't literally tackle.  Maybe in the sequel?

Regarding the annoyance factor, I wish I could tell everyone to be safe and rent the game.  If you use an online renting service that should be a possibility.  But if you go to one of the typical rental chains, it's doubtful that you'll be able to find it (Blockbuster does not carry many GBA games).  Unfortunately that means that to experience the fun you have to take a thirty-dollar risk.