I really took it in-house. The Constantine character has a kind of flesh-and-blood practical look at things that would seem, other people would use the word, occult or spiritual. But here, demons are real. So for me it was more taking it from the film itself. I didn't really need to go outside the piece itself to inform me because the perspective on it, what the character does, was provided by the script.
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be. Design is how you treat your customers. If you treat them well from an environmental, emotional, and aesthetic standpoint, you're probably doing good design.