Game designer Koji Igarashi is a pioneer of the Metroidvania game — these titles, which include his own Castlevania: Symphony of the Night, are action adventure hybrids mixed with exploration elements and lots of backtracking through levels to find additional content. Speaking at GDC today, Igarashi detailed his career in video games and what he thinks makes a good Metroidvania experience.

Igarashi said in game development, too many action franchises fall into the trap of catering only to mature, dedicated fans. This results in the company making changes that spike the series' difficulty level and heighten the barrier of entry for new players. When working on the Castlevania series, Igarashi said he and his team strove to make changes that would be more welcoming. The team wanted to remove the stress on players by implementing a more comfortable set of controls.

The team began building an exploration-focused side-scroller with a setup similar to The Legend of Zelda. The team decided to add a progression system that would level up players as they defeated enemies, as well as one that allowed them to capture monsters in order to flesh out a map.

"We looked back at older titles and we had non-human players that possessed transformation abilities," Igarashi said through a translator. "That's how we settled on our main character. But I had to stop and think about — where did this fit in the story's timeline?"

"It's vital to place importance on the experience of first-time players"

Igarashi explained the team began creating a new story that accommodated the main Castlevania timeline, but glossed over any inconsistencies between it and their own creation. The team also decided to give the game's visuals a fresh coat of paint, changing the game's look and feel from the main Castlevania line.

Because the game would be exploration-based and require a large map to accommodate many enemies, the team decided not to make the game in 3D. It would have been too difficult to render that many assets at once, and the team wanted to maximize the quality of the assets they were making. Also, the team had two very experienced 2D programmers, which made the move to 3D inefficient. So while the game was being prepared for the first PlayStation console, it was being done in 2D, despite the PSOne's poor quality of playing 2D games.

Igarashi also shared his guidelines for making good Metroidvania games. Developers must make it fun to control the player character and eliminate any potential points that would make it feel stressful; this must also be the same character from start to finish, although players should be able to unlock and equip new items to change up the available actions. Maps must also promote exploration, but not be completely free. There are limits, Igarashi said — if the player simply clears a game, maps that have been created with a single path don't promote revisiting. Revisiting areas can be a burden, unless players are determined to unlock every last item. Players that do revisit areas should be rewarded with new items.

"The bosses are the stars of the game."

Placing these Metroidvania moments early on in the game will keep players' attention; if they see the game opening up right away and know there are other branching paths to explore, they will be more likely to stick around and try those new paths. One trap developers fall into with this, he said, is placing puzzles in inconvenient areas and not properly communicating to how to access these puzzles. What seems obvious to a developer is likely as obvious to the player, so visual cues need to be placed around an area — this can be a display message on the map or something in the environment indicating how to progress.

"It's vital to place importance on the experience of first-time players," Igarashi said.

In terms of balancing out enemies, Igarashi stressed the importance of boss fights. Developers should focus on balancing boss fights and making them the best they can be, since "the bosses are the stars of the game." Igarashi shared his rue of thumb for making bosses: The boss programmer should be able to defeat the enemy without taking a single hit. That's how you know the boss was developed correctly, and it clearly demonstrates signals for how to defeat it.

Igarashi wrapped up his talk by expressing his wish to make more games like the ones described in his talk.

"I know I've been away from games in this genre for a while," he said. "But I hope things made sense. I want to believe one of the reasons why this speaking opportunity came up is because we're seeing less of these types of games and many fans are waiting for the next one. And now that I've gone independent, I can create things as I wish and not adhere to the company's wishes. If there is a desire, I believe I will be able to turn that into reality."

For more from Igarashi, check out our interview with him upon his recent departure from Konami.