The following is an excerpt from the upcoming book Legends of 16-Bit Game Development: A History of Treasure and the Sega Mega Drive / Genesis, which has been successfully funded on Kickstarter. The book tells the early history of Japanese developer Treasure and the games they released on Sega’s 16-bit console. If you enjoy this excerpt, please consider pre-ordering the book! -John Harrison

The Mega Drive is excellent. You see, the number of colors is limited and the sprite flicker can be severe. The hardware also doesn’t support things like background scaling and sprite transparency (unlike the SNES). And that’s what makes the Mega Drive wonderful. To avoid losing to other consoles, we developers have to push our skills to new levels and come up with all kinds of creative ideas. It actually gives us more motivation to succeed. When you reach a certain point, it becomes fun to consider the question, ‘How can we overcome the Mega Drive’s weaknesses?’

-Hideyuki Suganami1

Hideyuki Suganami and the Birth of Seven Force

When Treasure founder Masato Maegawa first brought the design proposal for Gunstar Heroes to Sega, a producer took one look at it and quickly rejected it, saying it would never sell. It was a repeat of what Maegawa had been told by his former boss at Konami—original action games were out of fashion. Maegawa, however, was not one to give up. He instructed the Gunstar Heroes team to develop a working prototype, something he could use to demonstrate the game’s merits. When the prototype was ready, he returned to Sega and once more attempted to persuade the producer to sign off on the project. This time, things were different. The producer was so impressed by the prototype, especially the second-stage boss Seven Force, that he quickly approved the project. Seven Force, designed and programmed by Treasure member Hideyuki Suganami over an entire exhausting month, was such a radical departure from the standard action game boss that it had to be seen in motion to be believed. As it turned out, Seven Force was just the magic that Treasure needed to convince Sega—and eventually the world—that Gunstar Heroes was something different, something special.

Treasure members in their office in Ueno, Tokyo in 1993. President Masato Maegawa is in the lower left, and in the lower right, designer Hiroshi Iuchi holds the maneki-neko statue that Hideyuki Suganami used as a substitute for himself in pictures. Source: Beep! Mega Drive, Oct. 1993.

Who was Hideyuki Suganami? His contribution was vital in defining the unique flavor of Treasure’s games, yet his personal background remains a mystery. He was deeply protective of his privacy and refused to appear in any photographs at Treasure, instead always substituting a Japanese maneki-neko (‘beckoning cat’) statue. However, his frequent writings and illustrations in the magazine Beep! Mega Drive reveal a highly eccentric, highly creative personality. Like most of Treasure’s members, he was an avid fan of video games, and he cited Namco’s Xevious and Compile’s MUSHA as two of his favorites.

An illustration by Suganami of his desk. Source: Beep! Mega Drive, Oct. 1993.

Suganami’s entry into the video game industry was unusual. Based on his training as an illustrator, he had first applied for a position as a graphic designer at Konami but was rejected. He then made the surprising decision to re-apply, this time for a position as a programmer. The catch was that he had no experience in—or knowledge of—programming. As Masato Maegawa described it, the hiring manager at Konami was impressed by Suganami’s persistence and decided to give him a chance, and so he was hired on as a programmer in 1990.

An illustration by Suganami of the imagined Team MDX. Source: Beep! Mega Drive, Dec. 1993.

Maegawa recalled the perplexity he felt when Suganami was assigned to work under him on Laser Invasion (NES): “I couldn’t understand why Konami had hired someone like that to be a programmer (laughs). He didn’t know anything about programming. My boss just said to me that since Suganami was such a cheerful, hardworking person, he should work under me.”2 While Maegawa handled most of the programming on Laser Invasion, Suganami studied and helped with what he could.

Suganami worked as programmer on one other game at Konami, Contra III: The Alien Wars (SNES), which was completed at the start of 1992. While working on Contra III,Suganami was exposed to many of the design principles that would later shape his work on Gunstar Heroes. The project was led by Nobuya Nakazato, a designer who was in his third year at Konami and who was the most senior member of the team (unlike many of his colleagues at the Tokyo office, Nakazato would not leave Konami to join Treasure; instead, he would stay at Konami and direct the classic Mega Drive games Rocket Knight Adventures and Contra: Hard Corps, among others). In addition to programming, Suganami also contributed art to the game; he would continue this dual programmer-designer role in future games.

Taka, the impressive first-stage boss from Contra III.

Contra III was developed at a time when the action game genre had reached a period of stagnation, especially in Japan, where RPGs had become the top sellers on home consoles. According to Nakazato, “the standard action game format up to that point—lots of weak enemies one after another, and then a short boss fight—was getting old.”3 In response, Nakazato, Suganami, and the other developers on the team brainstormed ways to revitalize the genre. “I wanted to make something,” said Nakazato, “where you could play through it without having to be prepared to really be in for the long haul each time you turned it on. And instead, make the content really dense… like music that you can listen to over and over again. Those were the sorts of things going through my mind, and that’s probably what led to it becoming a ‘boss rush’ kind of game.”3

One of the driving principles behind Contra III’s design was that, to keep the player engaged, there should be a steady flow of new events, obstacles, and challenges. Nakazato compared the idea to old horror movie taglines that advertised “a scare every however-many minutes.”3 He decided that an event of some sort should occur at least every three scrolls of the screen. As a result, most stages in the game featured a series of mini-boss encounters that happened in close sequence followed by a complex boss fight. The boss fights, which occurred while hanging from walls, riding motorcycles, jumping between flying missiles, and in other such situations, never developed a sense of repetition. Reduced, for the most part, were the multitude of waves of weak enemies that got progressively more challenging to clear. As described by Nakazato, Contra III was first-and-foremost a boss rush game.

Following the completion of Contra III, Suganami accepted Maegawa’s invitation and left Konami for Treasure. Initially, there was a lot of downtime for the new Treasure team. Lacking office space, they met at cafés around Tokyo to share their preliminary design work on Gunstar Heroes. Suganami used this time to develop many of the concepts that would drive boss design in the new game. These concepts showed a refinement of the work that he had done in Contra III, and more than ever they showed the fusion of Suganami’s artistic vision with his newfound technical skill.

As Suganami’s programming skills grew, Maegawa began to realize that he possessed a quality not often found in the average programmer: “He approached programming with the sense of a designer, and the end result was simply excellent. There are a lot of programmers out there that see character movement in terms of numbers, but for Suganami, he could express that character movement in a very natural way. A programmer who possesses that kind of sense is truly valuable. It doesn’t matter if they don’t understand what sine, cosine, and tangent are, if they have that sense, they can do great programming!”2

Suganami was drawn to the possibilities that existed within the use of multi-jointed characters. These were characters formed from small, repeating linked segments, most often found in shooting games in the form of a serpentine boss that flowed smoothly around the screen. Suganami was interested in the question of how repeating sprites could be linked together in more complex ways. There was a flavor of this exploration in some of the Contra III bosses that had multi-jointed limbs, such as the leg of the giant tortoise Taka, but the movement patterns were still simple. An advantage to using multi-jointed bosses was that they could be animated in complex ways through the program code alone, and this animation could be very smooth—at the same 60 fps at which the game ran. This would obviate the need to create memory-heavy sprite-animated bosses that moved less fluidly.

A serpentine multi-jointed boss from the arcade shooter R-Type (1987).

As he began work on the Gunstar Heroes prototype, Suganami became enamored with the Mega Drive hardware, especially its Motorola 68000 CPU. “The 68000 is great,” Suganami said in 1993. “It’s much better than the 65816 [the SNES CPU]. Its instructions are easy-to-understand, and it’s fast. When you do multiplication, you don’t have to jam a bunch of NOP instructions in there. The Mega Drive is truly a wonderful machine with a CPU like this.”4 On the SNES, it was necessary to include a series of four NOP (no operation) instructions—which do nothing but run two CPU cycles each—when using the unsigned multiplication function of the hardware.

Programming the movement of a multi-jointed character was tricky, since the positioning of each segment relative to its adjacent segments had to be known each frame. There were two general ways to do this, either through massive tables of data (known as look-up tables) stored in memory or through real-time calculations. Look-up tables were the simpler way of doing things. The relative positioning of each segment could be computed in advance, stored in the ROM, and then simply referenced when the character was on screen. However, Suganami was firmly committed to doing all of the movement with real-time calculations. “If you store all of the movement patterns as data,” he said, “then yeah, the processing is fast and the appearance is probably quite realistic, but that data is going to take up a huge amount of memory. I am firmly against this above all else. Multi-jointed characters have flavor because their movement is calculated in real-time!”5

Maegawa also emphasized the advantages of the Mega Drive over the SNES when it came to multi-jointed characters: “On the SNES, it was more difficult to implement lots of multi-jointed movement. The SNES wasn’t as good at multiplication, so you’d have to store character movement patterns as data. Since the Mega Drive was good at multiplication, you could do the movement calculations in the program. For the hardware of the time, that was a big deal. Multi-jointed movement on the Mega Drive looked very smooth.”2 Although both the SNES and the Mega Drive CPUs performed multiplication at similar speeds, the Mega Drive was capable of multiplying two 16-bit values together, while the SNES was only capable of multiplying two 8-bit values together (or, using its graphics processor, an 8-bit value and a 16-bit value). This may have limited programmers who were looking to do complex movement calculations using multiplication on the SNES.

The first mini-boss encountered on the first stage of Gunstar Heroes. Officially named Papaya Dance, it was nicknamed chinchin-hana (‘penis flower’) by the development team.

The prototype that the Gunstar Heroes team was working on contained the first two stages in the game—the Ancient Ruins and the Underground Mine. The team held nothing back. These two stages, packed full of content, had to act as a complete showcase to prove the game’s worth. In the Ancient Ruins, the player encountered the first mini-boss, a large balloon-launching flower called Papaya Dance, just 30 seconds into the stage. This simplistic mini-boss was actually constructed from a single static background layer. Using a line-scrolling effect, Papaya Dance appeared to vibrate wildly back and forth. The team nicknamed it chinchin-hana (‘penis flower’) due to its amusing shape and movement.

Papaya Dance was created from a static background image animated through the use of line scrolling. Each horizontal line of the boss shifted a certain amount when it was hit, giving the appearance that it was bouncing around. An alternating offset between each line also created a blur effect.

Papaya Dance demonstrated an important design feature that Gunstar Heroes shared with Contra III: adjusting the game’s difficulty level had big effects on how bosses operated. On Easy, Papaya Dance shot just a few balloons and posed no real challenge to even the most inexperienced player. On Expert, however, it shot out dozens of balloons as well as fast-moving caterpillar-like creatures. Without a clear strategy of attack, the player could easily die at this early point on Expert.

Bravoo Man, the second mini-boss encountered on the first stage of Gunstar Heroes.

Only 30 seconds after defeating Papaya Dance, the player ascended a pyramid and encountered the next mini-boss, Bravoo Man. This boss seemed to exist for one reason: to shout out to the player that they were playing something different, something worthy of praise. It was the ultimate showcase boss—it did not fit in with the theme of the stage whatsoever, but that did not matter because it looked incredible. Bravoo Man was a humanoid multi-jointed character composed of what appeared to be wooden crates or cardboard boxes. Its movement was fluid and smooth as it walked, jumped, and flew around the screen and made a variety of attacks (some of which bore a strong resemblance to certain attacks from Street Fighter II, of which Suganami was an avid fan). But what stood out the most was the 3D effect it demonstrated as it moved: each of the 16 boxes that made up its body and its head rotated—as if a 3D cube—in sync with the overall multi-jointed movement of the character.

The walking animation of Bravoo Man, in 10-frame steps (the frame number is indicated in the top right).

The 3D effect was so convincing that some commentators would later describe Bravoo Man as being made of textured polygons. The reality was nothing so complicated, however. Instead, the design of Bravoo Man combined multi-jointed movement with simple sprite animation. Each of the boxes making up the body was represented by a 24×24 pixel sprite, and each sprite had six variations resulting in six frames of animation. As the character moved, the sprite changed to create an animated effect. The cleverness of it was that the sprite animation was synced with the position of each box relative to the others to give the impression that Bravoo Man was lumbering across the screen in 3D. The 3D effect was broken, however, when Bravoo Man turned his body horizontally to fly through the air, since the sprites were only drawn to be vertical (but the speed of the flight was fast enough that most players would not notice!). The design was also very light on memory due to the low number of graphic tiles required to create it.

The sprites used to create Bravoo Man.

The multi-jointed nature of Bravoo Man allowed for an interesting difficulty level-based variation: with increased difficulty, the distance between each of the boxes making up the character also increased. The Bravoo Man on Easy was little more than half the height of the Bravoo Man on Hard.

The distance between each of Bravoo Man’s body segments changed depending on the game difficulty level. Left: Easy, Middle: Normal, Right: Hard (Expert was the same size as Hard).

Bravoo Man’s early appearance on the first stage seemed designed to impress, and it would feature prominently in many previews of the game. Rarely, if ever, had a boss character with such smooth animation and wide variety of movement patterns been seen in a console game up to that point. Maegawa, though, was quick to point out that it was not that technically impressive from a programming standpoint: “I often hear words like ‘skilled craftsmen’ and ‘technical masters’ used to refer to Treasure, but I don’t think that’s referring to our programming skills. Actually, in the company, we would jokingly call ourselves ‘skill-less Treasure’ (laughs). For example, with the multi-jointed bosses, we weren’t doing anything technically impressive in terms of programming. All we were doing was moving some sprites around. However, the way we displayed that movement and the ideas we put into it made it into something impressive. I think that’s what people are talking about when they say our games are amazing. If the way the characters move is fascinating, then it doesn’t really matter that our programming skills are lacking, does it?”6

Following Bravoo Man, the first stage ended with the boss Pinky Roader, a mecha piloted by the villain Pink and her two henchmen Kain and Kotarou. These characters were near-direct references to the villains in the classic 1970s anime series Time Bokan, of which the Treasure designers were fans. That series featured the beautiful villain leader Majo and her two henchman Grocky and Warusa. Grocky, the smart one, would build and pilot a different mecha each episode while Warusa, the strong one, would handle the weapons, and Majo would generally do nothing but boss her henchmen around. Each episode would invariably end with the villains’ mecha being destroyed in a huge explosion.

Pinky Roader, the first-stage boss of Gunstar Heroes, inspired by the villains of the anime series Time Bokan.

Pinky Roader was designed around a multi-jointed arm and two multi-jointed legs—each built from circular sprites—attached to a large body. Like its source material, the design was lighthearted and comical. The henchman Kain, being held in the mecha’s hand, zoomed around the screen at a fast rate while firing lasers at the player. Kotarou, piloting the mecha, frantically moved his hands around the controls and, when the mecha was hit by player fire, opened his mouth in surprise. Occasionally, the mecha took great lumbering steps, causing the screen to bounce up and down. The mecha’s feet were attached to its legs by large shocks that also bounced up and down as it walked. The action was frantic and the animation was smooth and impressive.

When defeated, each segment making up Pinky Roader’s arm and legs exploded in a series of fireballs.

When defeated, Pinky Roader exploded in a series of fireballs shooting out from each of the segments of its multi-jointed limbs. The explosions were rapid, scattering around in all directions as the screen flashed inverted colors. Suganami, in developing the game’s explosions, discussed being inspired by Compile’s MUSHA: “One of the impressive things about MUSHA is the attention to detail on the explosions. I love how the designers’ enthusiasm to make the game showy and gorgeous blasts forth from the screen. Sure, some recent arcade games have fancier explosions, but it’s the coarseness, the crudeness that makes MUSHA’s so great! They make an impression on you because there’s this buildup, this rising anticipation, and then it’s suddenly met by a massive launch of fireworks. If you’re exposed to it too much then you develop an insensitivity. Gunstar Heroes itself is very crude, but I’ve figured out some interesting ways to launch those fireworks, and I learned the basics of explosions from MUSHA. Explosions are kind of a bonus in a shooting game. They set the mood and really show the game’s personality.”7

The bosses of the first stage of Gunstar Heroes were undeniably impressive, but Suganami had something even greater in store for the second stage. On this stage, the player rode a fast-moving minecart that could switch between riding on the floor and ceiling or, in vertically scrolling sections, on either of the walls. Jumping between the minecart tracks was an interesting mechanic that added variety to the gameplay by increasing the player’s range of movement, and it also set up one of the most jaw-dropping boss fights of the generation: Seven Force.

The first appearance of Seven Force, piloted by the former ally Green, at the end of the second stage of Gunstar Heroes.

The concept of Seven Force came to Suganami shortly after quitting Konami, when he suddenly found himself with a lot of time on his hands. Ostensibly to research ideas for the new game he would be working on at Treasure, he had been watching a lot of television anime. “There was this one show called The Brave Fighter of Legend Da-Garn,” he said, “and it had a robot that changed between seven different forms. I thought, this is awesome! And I decided to make my own seven-changer, but as a multi-jointed character.”5

The seven forms of Seven Changer, Suganami’s inspiration for Seven Force, from the anime series The Brave Fighter of Legend Da-Garn. Source:

The Brave Fighter of Legend Da-Garn was a Saturday-evening children’s anime created by Sunrise and Takara that aired for 48 episodes from February 8, 1992 to January 23, 1993. The story featured a group of giant transforming robots that were tasked with protecting the Earth from alien invaders. Japanese toy company Takara, which in the early 1980s had created the original toy lines made famous by Hasbro as the Transformers, was selling a line of transforming Da-Garn toys concurrent with the television series. Partway through the series, a villain robot called Seven Changer was introduced that could transform between seven different forms. Why seven forms? It was a way of one-upping Transformers. In 1987, Hasbro had released the Transformers character known as Six Shot, which could transform between six forms, and in the following years several more six-changers were released. Da-Garn’s Seven Changer was the first toy to surpass the six-changers of Transformers.

The toy version of Seven Changer, created by Takara. Source:

The initial design proposal for Gunstar Heroes (then called Lunatic Gunstar), however, featured a slightly more modest boss called Five Changer. Everything else remained the same as the final release: on the second stage, the Underground Mine, the player encountered their former ally Green riding in Five Changer, and a boss fight ensued. The proposal was vague about the nature of Five Changer beyond saying that it had several different forms. An updated design proposal, developed after the game title was changed to Blade Gunner, saw the boss upgraded to one called Seven Changer. Seven Changer, it read, was the game’s ultimate selling point—a boss that could transform between seven forms. Sometime after that Suganami renamed the boss to the more original Seven Force and began to design the seven forms that it would take.

The initial version of Seven Force, called Five Changer, from the first design proposal for Gunstar Heroes (then known as Lunatic Gunstar). Source: Sega Ages 2500 Series Vol. 25 Gunstar Heroes Treasure Box.

Suganami spent an entire exhausting month on the process of designing and programming Seven Force. He recounted the ordeal: “After I decided to make Seven Force, then the painful days really began. I spent a long, confused month on it and it was finally finished. A whole month! Was I crazy?! I spent an entire month of our precious development period—as small as a sparrow’s tears—developing a single boss! Well, whatever. You’ll never see anything like it in another game. The way it moves is quite a sight. I wonder if I’m the only programmer in the whole world who has expressed the movement of a tiger as a multi-jointed character like this.”5

The forms of Seven Force were: Soldier Force (a running humanoid figure), Tails Force (a creature with a long, swinging tail), Tiger Force (a running tiger), Crab Force (a wriggling crab), Blaster Force (a handgun), Eagle Force (a flying eagle), and Urchin Force (a spiny, sea urchin-like ball).

The seven forms of Seven Force.

One of the compelling features of Seven Force’s design was that each form was built from the same few segments. The bodies were made with just five unique sprites—three circular and two asymmetrical—that were repeated in different overlapping patterns to create the particular form. In addition, there were four unique hand sprites and one head sprite. The color palette for each form was changed to further vary their appearance.

The segments used to design each of Seven Force’s forms. The color palette changed depending on the form.

All seven forms featured complex multi-jointed movement. Tiger Force, for example, had 19 independently-rotating jointed segments: six in each of its two legs, five in its abdomen/head, and two in its tail. Each of these segments moved at 60 fps, resulting in very smooth animation that was unlike anything seen on a home console before.

The Mega Drive did not have the ability to do hardware-based rotation effects, so to accomplish the rotation seen in each of the forms of Seven Force (aside from Crab Force, which did not rotate), Suganami used basic sprite animation. The three circular segments were straightforward: they did not rotate, but remained static throughout. The other two body segments, as well as the four hands and the head, were asymmetrical across both horizontal and vertical axes. To achieve a smooth rotation effect, each segment was drawn at a number of different angles—specifically, in 22.5° steps. That meant that sixteen sprites per segment were required to do a 360° rotation animation. However, because the Mega Drive hardware supported both horizontal and vertical sprite mirroring, it was only necessary to have eight sprites per segment in VRAM, each of which could be flipped over both axes to get the necessary sixteen.

All of the sprites used to animate the rotation of Seven Force’s parts. Each sprite is drawn in 22.5° steps. It is only necessary to have half of the 16 sprites needed for a full 360° rotation since the Mega Drive hardware could mirror sprites both horizontally and vertically.

With a 360° rotation requiring sixteen frames of animation, it was possible for Seven Force to rotate very quickly—up to almost four full rotations per second—and still remain smoothly animated. That rate of rotation could be seen on Blaster Force as it spun around a fixed point at the trigger (calling to mind someone spinning a handgun around their finger). On Expert difficulty, Blaster Force made two complete rotations and fired at the player once within the span of a single second, resulting in a very tense battle. Blaster Force also showed Suganami’s attention to detail. After firing twelve shots, the handgun paused its rotation to load a new magazine.

The most remarkable form of Seven Force was the humanoid Soldier Force. Although the order of appearance of the other six forms was randomized, Soldier Force always appeared first. It ran after the player in great strides and featured a variety of attacks, including one in which it launched itself into the air to throw spinning boomerangs, and another in which it slid across the ground foot-first. Soldier Force’s movements were striking for their realism, and the effort that Suganami put into this particular form clearly showed itself. He described discovering the movement pattern as follows: “I really got stuck on the running motion of the humanoid figure. I tried so many things but they never looked like a person running. Then, one day, I had to run home through the rain because I forgot my umbrella. In the middle of that heavy downpour, it suddenly hit me: This! This is the motion! Of course. From the beginning, I should have just tried running myself. But that moment was incredible. I owe my thanks to the rain. I was running through the downpour, laughing with joy. Being a programmer requires a lot of subdued, quiet determination, but the joy that you feel when the solution to a difficult problem flashes through your mind is unlike any other job.”5

The running animation of Soldier Force in 5-frame steps. Suganami discovered the movement pattern when he forgot his umbrella and had to run home through the rain.

As with other bosses in Gunstar Heroes, the fight against Seven Force changed significantly depending on the difficulty level. On Easy, the player only had to defeat three of the seven forms, and on Normal, five of the seven. Because the order was randomized, the player would have to play the game several times to see all of the forms. On Hard and Expert, however, the player had to defeat all seven forms. Furthermore, as the difficulty level increased, the rate of Seven Force’s attacks also increased, and the amount of damage the player inflicted with each shot decreased. On those higher difficulty levels, the fight became a brutal test of skill and patience as the player had to defeat seven full bosses back-to-back with no health recovery.

The great effort that Suganami put into the design of Seven Force paid off. Despite the initial hurdles, Sega eagerly approved the project once they saw the multi-jointed creations in action. Suganami, however, was not yet finished with Seven Force…



1 Beep! Mega Drive. Softbank, Jan. 1994, p. 83.

2 Continue, vol. 3. Ohta, Dec. 2001, p. 134.

3 Contra Anniversary Collection: The History of Contra. Konami, 2019, p. 28.

4 Beep! Mega Drive. Softbank, June 1993, p. 52.

5 Beep! Mega Drive. Softbank, July 1993, p. 56.

6 Sega Meisaku Album vol. 12: Masato Maegawa. Sega, 2004.

7 Beep! Mega Drive. Softbank, July 1993, p. 57.

Note: Feel free to re-post excerpts from this on your own website, but please link back to this page and credit the author, John Harrison.

All translations of Japanese sources were done by John Harrison.