Armin Gessert, CEO of Spellbound Entertainment and co-creator of Commodore 64 classic The Great Giana Sisters, passed away last Sunday after suffering a heart attack, according to online reports.

He worked in the video game industry for 25 years, shipping his first title, Street Gang (not to be confused with Street Gangs, the European name for River City Ransom), under Rainbow Arts in 1984.

During his time with Rainbow Arts, Gessert worked with Chris Hulsbeck and Manfred Trenz to develop The Great Giana Sisters, a charming but blatant Super Mario Bros. knock-off that won the hearts of many European gamers in the late '80s. He went on to found Spellbound Entertainment in 1994, releasing titles such as Airline Tycoon and the Desperados series.

"For many of us Armin, was a personal friend,” says Spellbound studio manager Andreas Speer (now acting as CEO), according to a note on the German developer's site first received by UK website Develop and also made available to Gamasutra by Spellbound representatives. “We still cannot believe that he has passed away. We will continue following Armin’s goals, as he would have wanted us to."

"I worked with Armin very closely for more than 15 years," adds Spellbound creative director Jean-Marc Haessig. "He was a good friend with whom I had a lot in common. Our visions of what to do to make our games great were absolutely the same. Though I will miss him bitterly I will continue to strive to create games that Armin would have been proud of."

Armin and Spellbound's most recent game, Giana Sisters DS, a well-received remake of the original C64 title, released in Germany and Australia earlier this year. It's unclear when and if the platformer will ship in other territories.