Design a VR-optimized 3D model of a dark fantasy medieval castle. The structure should feature tall, modular stone towers with gothic spires, detailed but performance-friendly textures, and low-to-mid poly geometry. Include high walls with crenellations, arched windows, and a central gatehouse with an iron-reinforced wooden gate. The castle should sit on a rocky cliff base with a broken drawbridge over a shallow moat. Add fantasy elements such as gargoyle statues, weathered banners, and faint glowing runes on the stone. Use PBR textures (2K or lower), include normal and ambient occlusion maps, and ensure LODs are available. Model should be lightweight and optimized for VR platforms like Oculus Quest— under 100k polys preferred, with clean UV mapping and no overlapping faces