When I spotted Gesuido, the first thing that caught my attention was the graphics. I was walking around this year's Busan Indie Connect Festival, eyeing all the games, looking for both the familiar and the unfamiliar, when I spotted a black & white image of a head in a sewer. The graphics were simple and pixel-based, but not like a console game from the 1980s. Instead, it looked like a game I might have played on my old (when I bought it) Macintosh Plus from 1992.

Imagine my surprise when developer Ryosuke Mihara told me he started making his game on a Mac — 18 years ago.

Gesuido (literally the Japanese word for "sewer") is an upcoming iPhone game that's a direct descendant of computer RPGs like NetHack. Mihara enjoyed those games in his youth and started messing around on his Mac at home to make a game like that for fun. That was in the year 2000. Eventually Gesuido turned from a lark into a real project, and Mihara has spent the last few years exhibiting it at local events like BitSummit in Kyoto and Tokyo Game Show as he puts the finishing touches on the game. His day job is computer programming but Gesuido is a personal project he's made by himself with additonal material made by an illustrator.

Gesuido features three playable characters, all represented on screen as a disembodied head: a samurai, a barbarian, and a programmer (a caricature of Mihara himself). The first time I played Gesuido I picked the programmer because I thought the image of a guy with glasses fighting gelatinous cubes in the sewer struck me as funny. I wasn't laughing when the very first cube I met killed me in three hits. It turns out I had inadvertently chosen "hard mode," as the other two characters start the game equipped with better weapons and stats. Why did Mihara code himself into the game as a weakling? "I'm not a warrior," he told me, laughing.

Starting again as a samurai, I found Gesuido a much more reasonable challenge, fighting my way to the fifth floor before succumbing to an angry wolf. As proper for a roguelike, the sewer in Gesuido is an original creation each time you start a new game. Your character's field of view is limited, and even explored space turns gray when your avatar leaves a room. For each action the player takes, the enemies also take one action, keeping things fair and rewarding patient play.

Even when playing as a non-gag character, Gesuido can be very tough. Traps can attack from out of view. Enemies can slide out of pipes. If your avatar is lit on fire,the player must find a puddle to extinguish the flames before their HP is exhausted. The hero automatically regenerates health over time, but also grows hungry. Eating food is not a means to restore health but to keep hunger at bay (my samurai wisely brought a bento into the sewer). Death means starting over from Floor 1.

"In European fantasy games, the heroes go underground and explore dungeons. In Japan, if you go underground there's nothing but sewers, so that's why I chose the name Gesuido" Mihara told me about the game's unusual nomenclature. When I asked why the game used distinctive western-RPG enemies like gelatinous cubes, he laughed again and admitted that the presence of such enemies were a legacy of the game's inspiration, NetHack. He asked me if I found the game hard to understand (it plays in both English and Japanese) but I told him I was already a fan of Shiren the Wanderer which made him laugh again.

Mihara hasn't settled on a release date yet (the Japanese press page says "in the not too distant future") or a price point, but he's positive it will be a paid app as he feels the gameplay does not lend itself to a free-to-play format. I'm going to keep tabs on Gesuido because there's a shortage of quality games I can play one-handed during my commute, with or without permadeath.

• rpg
• indie
• busan indie connect
• gesuido
• roguelike