**Building Core Structure**

I'm focusing on establishing the foundational HTML for the project, specifically the `index.html` file. This will serve as the canvas for integrating the `tone.min.js` library, setting up the piano keyboard interface, and managing user interactions.

**Designing Interface Elements**

I'm currently sketching out the visual layout in `index.html`, aiming to build a dynamic piano keyboard. This includes defining the structural `div` containers that will house the individual keys, setting the stage for both mouse and keyboard interactions to drive the sound synthesis.

**Implementing Piano Functionality**

I've successfully set up the `index.html` and styled the piano keys with distinct looks for white and black notes, plus an `.active` state for interaction. The JavaScript is now employing `tone.min.js` to construct a `Tone.Synth` with an ADSR envelope, and I'm dynamically generating elements.

**Finalizing Piano Implementation**

My thought process has concluded; the piano functionality is fully implemented. The HTML and CSS structure the visual interface, while JavaScript, leveraging Tone.js, handles note synthesis, keyboard mapping, and interaction feedback, completing the project.