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. Build an A/B loop-boundary experiment with one of the supplied 20-second environmental loops. Let me hear a hard repeat and an overlapping crossfade repeat. Show where the seam happens and let me jump to just before it, so I don't wait twenty seconds each time. Let me set the crossfade length. Keep levels comparable. Add a short generated texture with a deliberately poor join so the difference is easy to hear. Explain that an already seamless sample may not reveal a big difference.