Great shoot-'em-up with tonnes of great action and tight control.
Astro Boy is a short game but the action is so great you'll want to play through again and again, the control is very tight and responsive and there is'nt a single section that feels unfair. You can play it through on 3 difficulty levels and the difference is quite extreme, but it always is a tough game, the sort of tough that is simply fair and satisfying.
The game also has an interesting character progression system where you earn upgrades by meeting characters. All of these are characters from the show that fans will likely recognise. You can spend these upgrades on one of seven different abilities that each increase Astro's performance. Hunting out characters adds quite alot of replay value to the otherwise 3-6 hour game, and most of all it's fun.
Astro Boys graphics are simply excellent. Osamu Tezuka's distinct art style simply breathes out of every corner. The colour palette looks gorgeous and the games animations look fantastic. Although there are parts when the game's frame rate really bogs down, which can be bizarre on the tiny portable.
But Astro Boy is still a great, action-packed side-scroller, and easily one of the greatest games on the GBA.