Among shmup fans, Seibu Kaihatsu is known for the Raiden series. INH, the preeminent STG superplay producer, released a Raiden III superplay in 2006 that featured this Viper Phase 1 interview in the liner notes (and another, longer interview about the entire Raiden series that I’m currently working on).

The second interview from 1997 was found at the GSLA and is unsourced, but talks a bit about Seibu Kaihatsu’s penchant for realism in their games. There’s also an intriguing mention of a Saturn port of Raiden Fighters which sadly never came to be…

Seibu Kaihatsu homepage
INH Raiden III superplay

2006 Viper Phase 1 Developer Interview

with Yoritaka Kasai of Seibu Kaihatsu and MOSS

—First off, can you tell us what your role was in the development of Raiden III?

Kasai: I didn’t directly take part in it. My main work at MOSS at that time was internal infrastructure, server maintenance, network security, etc. With Raiden III I did help out on debugging and publishing work. I captured screenshots from the game for the homepage and for promotional materials. For the port, I reached out to and worked with the superplayers.

—How did you end up joining Seibu Kaihatsu?

Kasai: There were two reasons. First, the timing was right. I had just quit my last job and applied to Seibu. Second, the company I had worked for published Raiden.


Viper Phase 1, aka “Raiden in Space.”

—Can you tell us the details of the games you worked on at Seibu Kaihatsu?

Kasai: Sure. On Zero Team, I handled all the programming outside of the main game system: zako, bosses, and the player controls. You could say I did all the tuning for the game to make it match the initial design.

On Viper Phase 1 I did all the programming, including the game system, bosses, and zako.1 I remember struggling with the hardware limitations of the first CPU and first PCB we used. I worked a lot on tuning the enemy placement, strength, and resilience. I also went on a business trip overseas and made many adjustments afterwards specifically for the overseas market.

Raiden Fighters was mostly the same as Viper Phase 1. There were no struggles with the hardware this time, but on Viper Phase 1 I didn’t have much opportunity to optimize the game system’s performance, so I did a lot of that with Raiden Fighters. I also programmed background bosses, as well as a raster scrolling-ish system (a first for Seibu). Saitou2 handled most of the game balancing so it was a pretty relaxed project for me. All I did for balancing was weapons and bosses.

I was working on another project when Raiden Fighters 2 was being developed. The schedule was very tight, so I was only able to help out with programming the ending.

—Why is it that on stage 4 of Viper Phase 1 NEW version, even after you destroy all the enemies on that level you can never get the 100% bonus?

Kasai: When the screen scrolls past a certain point the system deletes enemies that would have otherwise spawned but were out of range. On stage 4 of the New version I added some new enemies, but I entered the wrong spawning coordinates for them, and the moment they appear they’re deleted by the system, effectively acting as if the player had not destroyed them. The Old version has the same bug on stage 6. It was my mistake.

—I think Viper Phase 1 and Raiden Fighters, following in the footsteps of Raiden, do a masterful job of balancing general accessibility with elements that appeal to more hardcore scorers. Was that something you consciously strove for in the development?

Kasai: I didn’t think about scoring systems much when I was making Viper Phase 1. The destruction bonus was something I added more to get players thinking along the lines of “destroy them all!” In the NEW version I added the medal element since the American market seemed to like collecting items.


The first boss in Raiden Fighters.

As for Raiden Fighters, you probably know this already, but that scoring system was heavily influenced by Saitou.

Making our games accessible to players was something everyone was very concerned with at Seibu Kaihatsu, not just me. Games needed to be simple, easy to understand, balanced, and fun. Then they would be well-recieved by a larger audience.

—Did you work on the Playstation ports of Raiden Project or Raiden DX?

Kasai: No, I didn’t. I remember they had a hard time with the very strict deadlines for those ports. By the way, the Raiden Project title font was the main programmer Oku’s actual handwriting.

—Do you have any other interesting episodes to share with us from your time at Seibu Kaihatsu?

Kasai: Making your games accessible to the general public on the one hand, while also having hardcore appeal, are two opposite goals. Making those work together in a single game was very difficult.

As a developer Seibu Kaihatsu was always very conscious of the overseas market, too. We never sold that well in Japan but overseas our games did very well. Zero Team and Seibu Cup Soccer are good examples. In order to balance the games for a western audience I went overseas, and was outside of Japan for awhile. That experience also led to me joining a Korean game developer in 1998.

—It’s been 7 years since the release of Raiden Fighters Jet. Having joined MOSS, what did you think when you heard another they were going to make another Raiden game?

Kasai: I was worried. The times have changed, so you can’t release a game that’s the same as those old days. At the same time, if you change things too much it won’t feel like a Raiden game. It’s a dilemma. I feel like Saitou did a good job though.

—For my last question, I’ll ask straightaway: what does the Raiden series mean to you?

Kasai: “The gold standard for accessible STG”… something like that? Of course, most people can’t clear the whole game, so saying “accessible” here might sound a little strange. But hey, it’s an arcade game after all.

Nowadays there’s so many games that require you to read the instructions before playing. Raiden is a game where you need no foreknowledge, and even if you can’t clear it, it should still be fun to play. There’s already enough games out there that practically require you to study before you can even start them.

1997 Seibu Kaihatsu Developer Interview

Shuuichi Mori – Managing Staff
Yoritaka Kasai – Programmer

Origins of Seibu Kaihatsu

Kasai: Our first STG, Stinger, came out in 1983. I don’t think anyone remembers it today though. (laughs)

Mori: That was an isometric view STG, right? (laughs)


The original Raiden.

Kasai: Our flagship work, of course, is Raiden, released in 1990. Thanks to it we were able to attract a lot of STG fans to Seibu Kaihatsu, and with the great increase in STG fans, we continue to make them today. Raiden was easy to understand, it felt cool just shooting the laser, and the screen would get hectic and covered without bullets despite not being a bullet-hell. Those are the things that made it so fun for players, I think.

As for the difficulty, we would have been fine making it easy enough that men and women of all ages could play it, but being an arcade game, if people play too long it’s bad for business. So we were forced to make Raiden a difficult game.

STG Realism

Kasai: We wanted to make the graphics less anime-style and more realistic. Aside from Viper Phase 1, all our STGs feel like they take place in real environments. We also keep the controls standard: button 1 is shot, button 2 for bomb. Raiden Fighters also has a charge shot, but it’s perfectly playable without using it.

The processing speed and the number of colors you can display have both gone up on recent pcbs. The new mother casette system we’ve adopted can put out 4x as many colors as before. And the increased graphics capabilities has also meant an increase in ROM storage.

Cannons and guns, for instance, can now be rotated smoothly instead of the choppy frames of before. We fuss over little details like that a lot. It’s easy to just use hardware based sprite scaling or rotation, you know, but if the shadows don’t also rotate then it looks ugly. All the designers at Seibu Kaihatsu take great care with shadows. It takes a lot of time but it ends up looking more realistic.

Similarly, it’s now possible to program big enemy sprites that move very quickly, but who would be satisfied with that? So we make big enemies move slowly, and small enemies move quickly. This realism has been our stance since the first Raiden, and it hasn’t changed one iota.

As far as difficulty goes, we do all the playtesting in-house. But everyone at Seibu Kaihatsu loves STG, so it has sometimes happened that we release a game to the public and it’s too difficult. We also send staff employees to the game centers to see how players are receiving the game.

In the future I think the entire game industry will be shifting towards 3D, but I think a 3D STG would be confusing to players, so I expect the 2D STG genre will keep going strong. We might try to make a 3D STG at Seibu Kaihatsu sometime, though.

Console Ports

Mori: The hardware specs for our games are very high, so it’s difficult to port them to consoles. It would take too much time. And we don’t want to do a half-assed job, either…


Model of the Raiden MkII.

Kasai: We put so much love into the originals, we’d want to put the same care into the ports too. But we can’t. For now we have to refuse.

Mori: The arcade and consoles aren’t so different in terms of hardware power, it’s more that they’re oriented to different things. CD-ROM systems have lots of room for memory, for instance, but they also have loading times.

Kasai: We have presented plans for a Saturn port of Raiden Fighters to Electronic Arts, but it’s up to them. I think it will be very difficult to do. (bitter laugh) Though the Saturn is easier to develop for when it comes to STG.

Mori: I wish we could do the port ourselves.

Kasai: Yeah, if only someone would release a console that’s easier to do 2D on. I think Sega will come up with something. The next generation will be the age of polygons, but we can’t forget about 2D. I think that’s why the Saturn has so much memory capacity.

Anyway, please look forward to the Saturn port of Raiden Fighters from Electronic Arts, as well as Raiden Fighters II which is in arcades now. We’ll be doing all we can at Seibu Kaihatsu to give you quality and quantity.

Mori: And if you see our games installed somewhere, please be sure to play them. (laughs)