The original 1997 design document for Deus Ex privileges character development over all other features.[37] The game was designed to be "genre-busting": in parts simulation, role-playing, first-person shooter, and adventure.[36] The team wanted players to consider "who they wanted to be" in the game, and for that to alter how they behaved in the game.[34] In this way, the game world was "deeply simulated", or realistic and believable enough that the player would solve problems in creative, emergent ways without noticing distinct puzzles.[34] However, the simulation ultimately failed to maintain the desired level of openness, and they had to brute force "skill", "action", and "character interaction" paths through each level.[46] Playtesting also revealed that their idea of a role-playing game based on the real world was more interesting in theory than in reality,[47] as certain aspects of the real world, such as hotels and office buildings, were not compelling in a game.[47]