Uses 3D graphics instead of 2D, and adds a new kind of reflect attack, the Reflect Laser. Also introduces the "volcano" mechanic: if enough medals are on the screen, a "volcano" of medals will erupt, producing even more medals. The Dreamcast port adds a 4-player option, a rarity for a shoot-em-up.
1-Up: There is one available in item form near the end of the fourth stage. However, it won't appear unless you've died at least twice by that point (which on default settings means you're on your last life).
Bittersweet Ending - Giga Wing: Your character sacrifices himself or herself to destroy the Medallion. In order to avert this ending, you must beat the first six stages on one credit to see the true final stage (and boss). Beating the game with two players will also avert the need for Heroic Sacrifice.
Bullet Hell - But by employing the Reflect Barrier properly, you can turn it into Bullet Heaven.
Cap - The maximum multiplier in the first game is 49,999,999 which can be reached near the end of the game by very skilled players. In the second game, the maximum multiplier is 999,999,999; this can be reached in the third stage out of 7 with skill. Amazingly, the score caps in any game are nigh unreachable.
In the second game, there is a cap of 110 medals on screen as well as an unknown total object cap; reaching either will cause an item volcanon, where the background will go black and then each medal will split into 10 or more kite-shaped medals.
Color-Coded for Your Convenience - In the first two games, the lowest 8 digits of your score are colored blue, the next four yellow digits (the oku places) are yellow, the four digits in the chou supergroup is colored red, and (in the second game, where such scores are possible) the digit(s) afterward (kei) are cyan*
In Japan as well as all of East Asia, supergroups of four digits are common rather than supergroups of three digits as in Western society; rather than thousand, million, ... their supergroups go man (ten thousand; 10^4), oku (one hundred million; 10^8), chou (10^12), kei (10^16) and so on.
. Generations uses a different color scheme (red for kei, yellow for chou, green for oku, gray for anything smaller).
Cultural Translation - The kanji used as separators for every fourth digit in the player's score were removed in the US releases of the games. The US releases don't even bother to replace the kanji with commas, so reading scores in the US versions is a bit trickier.
The US version of Giga Wing 2 uses commas when displaying the player's score at the end of a stage, though still has the myriad-based (supergroups of four digits as is common in east Asia; see above) color-coded digit groupings otherwise.
Score Multiplier - The core of this game's scoring system. Each medal will add its own value to the value of every medal you've picked up so far on your current life or stage, and that will be added to your multiplier. For instance, picking up a +5 at the beginning will add 5 to your multiplier. Picking up another +5 will add 5 to your medal count for 10, and 10 will be added to your multiplier. By the end of most stages, each medal will usually be adding thousands to your multiplier at a time. Even in the first game, a good player will have multipliers in the millions.
Scoring Points - One of the main highlights of the game, in a subversion of score being regarded as a pointless number. How often do you see scores of at least 1 trillion?
Self-Imposed Challenge - Some players try to go for the lowest score possible, or go as far as possible without scoring at all.
Sequel Escalation - Each game ups the ante with more medals to collect and thus more points to be had. Giga Wing's 15 digits? Nothing compared to Giga Wing 2's 17 digits...which in turn is surpassed by Giga Wing Generations, quite possibly the only commercial game where you can achieve 20-digit scores.
True Final Boss - Two of them, in Giga Wing: the black ship you've been chasing, and the Medallion. Both are fought simultaneously.