"Sonic the Hedgehog" was developed by a team of seven: two programmers, two sound engineers, and three designers, although it began with just Naka and Ohshima. People came onto the team as the need for content increased. After being assigned a project with the code name "Defeat Mario", Naka and Ohshima began work, but encountered problems: Ohshima's Rabbit proved hard to program. Catching items and throwing them caused the action's rhythm to break. Naka stated that the rabbit was not suitable for his game engine, and he also wanted the game to be playable with only one button. Hirokazu Yasuhara came onto the team to supervise Naka and Ohshima and develop levels. He became the lead designer due to his greater experience, and found the way to make the game playable with only one button by having Sonic do damage by jumping. The trio came up with the idea of him rolling into a ball. After the hedgehog character was chosen, many characters were redrawn, and the team agreed on the environments' visual complexity, with particular focus on the colors. After this, four people came onto the team to speed development up.