Prompt: Write a short story about a man who discovers a magical portal

Gregory opened his eyes to a bright world of unfamiliar colors. He felt a wave of dizziness and closed his eyes again, but when he reopened them the colors were still there. Gregory tried to sit up, but his head pounded and he found himself lying on his back on the hardwood floor. He groaned and tried to move his arms and legs, but they felt like lead weights. Gregory realized he was in some kind of magical portal and he began to panic. Suddenly, the world began to spin and Gregory blacked out.