In the Tetris domain visualization, each object is represented by a specific geometric shape and color to convey its type, status, and position within the grid. The grid itself is composed of individual squares which form the backdrop for the Tetris pieces. Here's a breakdown of the visual encoding:

1. **Shapes and Sizes:**
   - **One-square piece:** Represented by a single square. This shape is used to signify that the piece occupies one grid cell.
   - **Two-square straight piece:** Not applicable in the initial state but would be represented by two adjacent squares in a straight line, either horizontally or vertically.
   - **Right-L piece:** Represented by three connected squares forming an "L" shape. This signifies that the piece occupies three positions in an "L" configuration.

2. **Colors:**
   - Each piece type is assigned a distinct color to differentiate it from others. For example, single-square pieces might be red or yellow, while "L" shaped pieces could be blue or green.
   - **Occupied Status:** Colors are used to denote the occupancy status. For instance, red or yellow for occupied squares, indicating they are not clear.
   - **Clear Status:** The grid squares that are not occupied by any piece are left uncolored or given a neutral color like white to signify they are clear and available for movement.

3. **Text Labels:**
   - Each piece and grid cell has a text label indicating its identifier and status. This text is placed within the shape and is positioned to avoid overlap with other elements.
   - The text for the piece identifier is positioned slightly higher within the square to ensure it does not overlap with the status text.

4. **Legend:**
   - A legend is included to map colors to statuses, ensuring clarity in the visualization. It provides a reference for understanding what each color signifies in terms of occupancy.

5. **Bold Edges:**
   - The outer edges of each piece are bolded to distinguish them from the grid lines, emphasizing the boundaries of the pieces.

6. **Contrast and Readability:**
   - High contrast between text and background colors is maintained to ensure readability. Text colors are chosen to stand out against the piece's color or the grid's background.

7. **Placement and Layout:**
   - The layout ensures no overlap between objects, and text is clearly visible. The grid is organized in rows and columns to mirror the Tetris grid structure.

This encoding ensures that the diagram is intuitive and that the status, type, and position of each object within the Tetris grid are immediately apparent to the viewer.