I'm a product design student. I'm not familiar with the terminal or writing code. Please build this for me with HTML, CSS, JavaScript and native Web Audio. Make a simple, usable browser page, with no external libraries or internet services. Sound should start only after I click. Use comfortable initial levels. I need to play with the result, not read code. Extend the scene-based sound machine with a sleep timer and a gradual fade. I can choose the duration and fade length, see the countdown, cancel it or restart it. At the end nothing should return: stop loops, notes, events, movement and effect tails. Add a ten-second demo so I can test it without waiting. Cancelling a fade should restore a sensible listening level. Keep the City, Forest and Water scenes. I want a calm, usable listening experience, with the detailed engine controls still available.