variety. The fading visibility in ShadowCaster was improved by adjusting the color palette by distance, darkening far surfaces and creating a grimmer, more realistic appearance. This concept was also used for the lighting system: rather than calculating how light traveled from light sources to surfaces using ray tracing, the engine calculates the "light level" of a section of a level, which can be as small as a single stair step, based on its distance from light sources. It then darkens the color palette of that section's surface textures accordingly. Romero used the map editing tool he developed to build grandiose areas with these new possibilities, and came up with new ways to use Carmack's lighting engine such as strobe lights. He also programmed engine features such as switches and movable stairs and platforms. In the first half of 1993, Carmack worked on improving the graphics engine. After Romero's level designs started to cause engine problems, he researched and began to use binary space partitioning to quickly select the portion of a level that the player could see at any given time. In March 1993, the team stopped work on Doom to spend three weeks building a Super Nintendo Entertainment System port of Wolfenstein 3D, after the contractor hired for the port had made no progress. Taylor, along with programming other features, added cheat codes; some, such as "idspispopd", were based on ideas their fans had come up with while eagerly awaiting the game. By late 1993, Doom was nearing completion and player anticipation was high, spurred on by a leaked press demo. John Carmack began to work on the multiplayer component; within two weeks he had two computers playing the same game over the internal office network. Soon, the office was playing four-player deathmatch games. Graphics and sound Adrian Carmack was the lead artist for Doom, with Kevin Cloud as an additional artist. Additionally, Don Ivan Punchatz was hired to create the package art and logo, and his son Gregor Punchatz created some of the monsters. Doom was the style of game that Adrian Carmack had wanted to create since id was founded, one with a dark style and demons. He and Cloud designed the monsters to be "nightmarish", and developed a new technique for animating them. The intent was to have graphics that were realistic and dark as opposed to staged or rendered, so a mixed media approach was