Create a visual representation of an autism center situated on a scenic hill surrounded by lush pine trees. The design features a four-story building on the left, specifically designed as sleeping units for patients. This section should appear serene and comforting, emphasizing the restful atmosphere, and be constructed from concrete for a sturdy yet inviting look. In the center, depict an elongated two-story activities building made of concrete that connects to the first two floors of the sleeping unit, showcasing spaces for various therapeutic and recreational activities with thoughtfully placed openings to express the interiors rather than traditional facades. To the right, illustrate a cafeteria building that juts out perpendicularly, featuring fewer facade windows but incorporating large openings that create a welcoming atmosphere and showcase the views, also constructed from concrete. As you move upward, show the building gradually becoming more accessible to the public, with strategic openings that differentiate the spaces while maintaining a cohesive design. At the rear, design a welcoming entrance that seamlessly integrates with the overall block, creating an inviting access point for the entire project. Focus on creating a harmonious blend of functionality and tranquility, reflecting the purpose of the center.