With a game like Outer Wilds, it has been critical for us, the designers, to work closely with the art team when it comes to the creation of the levels. First, because a large part of the game is told through environmental storytelling. Secondly, with a game about player-driven exploration, visually guiding the player towards points of interest is vital.
One of our biggest challenges is to ensure players never end up lost in an environment for a few minutes before finding what they are looking for. As there are no markers on the screen or minimap as to where things are, the content needs to be immediately identifiable when arriving in a new area. The last thing we want is to make the players feel like they need to check every corner in case we hid something there.
The start of that collaboration comes with us using the concept art our art team created as a visual reference for our graybox. When I start designing a place, I like to reproduce a crude version of the concept art look. It keeps me within the visual constraints of the game and often inspires new level design ideas.