This port is actually a cancelled one but at the same time, an original one.
For a deeper analysis of Darius, check the following link: viewtopic.php?f=10&t=66104 (Also covers Darius Plus and Super Darius)
'Nuff Said about this port of Darius.
This unreleased port of Darius which is an exclusive of the Megadrive Mini, is the most arcade-perfect port in gameplay terms. To begin with, the screen resolution of the Genesis helps a lot since it is much wider than the PC Engine, allowing a wide range of movement in the game and making the game less difficult that it was originally meant to be. Like the PC/CD Engine ports, the game is only limited to 1-player only. To compensate that, Taito relied on a gameplay mechanic from Sagaia/Darius II: Allow the player to choose to play with Proco or Tiat.
Playing with Proco is basically the original arcade game difficulty since the power up bar is resetted if you lose a life, while selecting Tiat doubles the Silver Hawk's firepower and allows the player to keep their Power Up power levels if they lose a life. However, you can't enter the Ranking if you die or complete the game as Tiat. One of the major changes from any other console port of Darius and even the original arcade version was the instant respawning after losing a life. Unlike the original game where you were kicked back to a checkpoint after dying (or restarting the boss fight), you will respawn immediately, making the game a little bit more "friendly" in difficulty. This comes in handy when you're playing as Proco. The game also have variations in the stages because some levels grant you more items than the PC Engine port and the new bosses are more difficult.
Yeah, I said new bosses, 'cos the game allows us to select an incredible "Special Feature": Select if we want to play with the "Arcade" boss order or "26 Bosses", Arcade is the traditional "Dual Shears in Zones D-E-F, Fatty Glutton in G-H-I-J, etc.", and 26 Bosses improves the list removing repetitions by adding the bosses from Super Darius like Tough Spring in Zone M, Driosawm in Zone P, and adds Big Rajarnn in Zone D. Playing the game with this boss order is with no doubt "The Definitive Darius Experience" that both Darius fans and newcomers were looking for.
If you lose all your lives, there's no continues because there's no cheat codes known for this port, and I think that's for the best because if you remember the continue code in Darius Plus, it resetted your weapons to the lower levels, making the whole continuing more difficult than expected at the point of making you think it was more convenient to start all the way back from the beginning.
Darius: All for Fun and Fun for All!
Next stop: Playing Gridseeker, have a burger and go home.
Unlike Super Darius, the Genesis version restores the original ending of Zone Y like the arcade version, adding the humorous gag of the battle was a game. Why NEC ommited it in the CD Engine?, I have no idea.
To complete the enhancement of Darius, there's an alternate game mode called Boss Rush Mode, which is a more complete version of what Taito brought on Darius Alpha and the hidden Boss Rush mode in Super Darius since it allows you to play go against the 26 bosses comprising both Arcade and Darius Plus bosses. Unlike Darius Alpha, rather than getting 3 or 2 instant level ups after each boss fight, you're granted 1 power up item for your weapons and shield. Like in Darius Alpha, if you lose all your lives, there's no way to continue the game. Well, there's an option that allows you to start from Zone A to G, but this is not too much of a good idea since your power levels are totally resetted you'll be overpowered by My Home Daddy, Fatty Glutton and Guard Savage (even if you play this mode as Tiat).
Watch the birdie! *"Top Gun Anthem" plays in the background.*
Boss Rush Mode included its own ending, which is the Zone Y ending of Super Darius (2-Player Zone V in the arcade) where Proco and Tiat merge their Silver Hawks to form a bird and crash with what appears to be a core or a base, but this time is rendered in an arcade like color palette.
My best theory of how would be the cancelled port would be like is the game would comprise of the original game and the default "Arcade" boss line up, but for the MD Mini port, Taito and M2 decided to add the Boss Rush and the "Arcade or 26 Bosses" options, making this game an improved version of what was once a cancelled port. You can call it "Darius Enhanced" if you want to, or even "The Real Darius+" since its definitely a plus over the Amiga/Atari ST and PC Engine ports.
Graphically, gone are the days of the eye-hurting, way-too-bright colors of the PC Engine/CD Engine Darius Plus and Super Darius versions. There's no difference between the Arcade and the Genesis port. All the original arcade color palettes and even the visual effects are present in this console port like the mini-swirls that reveals the screen of the game when we start playing, the lightning effects in some stage backgrounds, the flashing purple "sky" in Zones A and P and even the Shield glowing effect. The original arcade bosses have their correct arcade colors, even the arcade cancelled Big Rajarnn uses its intended arcade sprites, while others like Guard Savage, Little Stripes and Tough Spring keep their PC Engine ones, just like in Darius R this is one huge improvement compared with the Genesis port of Sagaia/Darius II which had its graphics and color differences despite being a great port of Darius II.
Back then, the Genesis box claimed its 16-Bit Power had "ARCADE GRAPHICS AND SOUND" and "NEW DIMENSIONS IN GAME PLAY" and as a testimony of those claims, Sega included Altered Beast. But as most ports of arcade games, it differed in both graphics and sound like Raiden Trad, Truxton and Vapor Trail: Hyper Offence Formation. Another example of this "Coin-Up Conversion Dilemma" was Street Fighter II' Special Champion Edition which was heavily criticized by its fans due to the game's terrible quality in graphics and the distorted PCM driver sound. While there's no specific reason behind those flaws, most people believes it was the console's limitations what brought the poor quality of the port.
We all know that most Genesis conversions made hard decisions between what to keep the most: Arcade-like Graphics like OutRun and Super Hang-On or have arcade accurate sound like After Burner II and Vapor Trail. Based on that explanation, Capcom tried to keep both in Street Fighter II's case. But a lot of Non-Arcade games like the Thunder Force series, Contra Hard Corps, the Amiga-like shmup Bio-Hazard Battle and Alien Soldier contradicts the theory since they feature graphics capable of compete with the big arcade titles of that time. In this age of romhacking, a new theory suggests something really unexpected: Capcom internally sabotaged Special Champion Edition to make the Genesis look inferior and give bad reputation to Sega due to the delay of the game release because of Street Fighter II Hyper Fighting's arcade launch and the subsequent SNES Street Fighter II Turbo release. This theory is currently backed up due to a ROM Hack called Street Fighter II' Hyper Champion Edition, formerly called Street Fighter II' Champion Edition Arcade which fixed the graphics, added missing scenery animations in many stages and it can be combined with a sound driver hack which fixed Capcom's garbled sound driver making it almost arcade perfect, proving the Genesis was indeed capable of higher quality graphics and sound unlike the non-hacked Special Champion Edition.
As for the sound, it is extremely faithful to the original arcade. Unlike After Burner II and OutRun which focused on the sound rather than graphics, Taito pushed the limits of Sega's hardware at the point of showing perfect arcade sound quality AND keeping the graphics. For instance, the fast "Taka-ka-kaka-ka-kaka-ka" percussion sequence in Zones K and Z is perfectly recognizeable for those who heard the original arcade soundtrack, something that NEC had to rely on the CD-based Super Darius (and Sega with After Burner II Complete and Space Harrier with the 32X add-on).
Remember the Nintendo-trolling "Genesis does what Nintendon't" commercial during the 90's?, the Genesis port of Darius is basically "Genesis does what Nintendon't and TurboGrafxn't" ("PC EngiNOT" or "NECan't" could work too). A perfect arcade conversion on a 16-bit console and a true testimony that proves the Genesis was much more capable of full arcade accuracy in both graphics and sound terms, breaking with everything we were used to know about console ports of arcade games.
It was a shame that the game was cancelled back then and saw the light decades later as an "Enhanced" game for the reasons I've mentioned before, but at least, the Genesis Darius line-up is finally complete.