I suppose it’s played like a game though the urgency suggests that the threats are real. But how can a half-dozen people locked in a 15’×30′ room really qualify as a civilization? No matter. When we detect the interlopers down the hall, we get the door slammed and barred before they can see us. But they know that we’re in here and they’ll try anything to get in. Just as we are prepared to make any sacrifice to keep them out. We grab rocks, bricks, blocks of wood — any kind of shim we can find in the closet and jam them under the door, anything to seal it up. Out in the hall we can hear them trying to work their way in. They’re trying to lower the floor. We hover near the door, holding our bodies up against it like that will make some difference. The room is filling with water? The water rises. We dive down to ensure that the shims are still lodged under the door crack. A hand comes through from the other side, we grab it and go at it with a bow saw. Cries of pain, the arm recoils. The water recedes some but there is damage and one of us has drowned. We wait for cries or even shuffling from the other side but it seems they have retreated. We are loathe to re-open the door.