I took designing the look of the levels to asset level on parts, especially if the assets had gameplay purpose which had to be told to the player. For the assets that had gameplay and animations included, I often worked in 3d to make sure the plan would carry over to gameplay or cutscenes. The mockups were tested in game and then later passed to asset artist to have their pass over the assets, once they were deemed to be suitable for their purpose. This helped to speed up the development process for the rest of the art team