Fun Fact: The programmers for Kid Icarus sometimes slept on cardboard boxes, covering themselves with curtains, within the development building in order to make the game's deadline!
Kid Icarus was an action platformer set in Angel Land, which was based on ancient Greek aesthetics. Players controlled a hero named Pit who had to kill monsters with a bow and arrow, and could collect the hearts they left behind as currency to buy items and upgrades. As the game progressed, Pit would collect key pieces of gear that would make him exponentially more powerful, like a crystal shield, flaming arrows, and a holy bow.
The game was split into three areas – the Underworld, the Surface world, and the Sky world. Each area was then split into three platforming areas for exploration, and a fortress that was more of a maze, with a boss Pit needed to destroy for one of the three pieces of gear that would eventually allow him access to the final level.
The Sky Temple at the end of the game was a scrolling shooter, not a platformer, which made the ending exciting as it was such a dramatic change from all the previous gameplay.
Kid Icarus wasn't the most powerful NES game visually at the time of its release, but it was bursting to the seams with style. The music was fantastic, and nothing else on the system looked like Kid Icarus at the time. It was also very challenging mechanically, and gave NES players a lot to sink their teeth into.