In the Tetris domain visualization, each object on the grid represents a Tetris piece or a grid cell, and their visual attributes (shapes, colors, labels) convey their identity, status, and relationships with other objects.

1. **Shapes**:
   - **Square**: Represents a one-square piece or a single grid cell. This shape is chosen for its simplicity and direct correspondence to the grid layout.
   - **L-shape**: Represents a three-square "L" shaped piece. This configuration visually conveys the piece's unique arrangement and orientation on the grid.

2. **Colors**:
   - **Blue**: Assigned to the "L" shaped pieces to distinguish them from other pieces. It indicates that these pieces are part of a larger structure.
   - **Green**: Used to represent another "L" shaped piece, providing visual differentiation between multiple "L" pieces.
   - **Red**: Represents a one-square piece, indicating its unique identity and status as a single unit.
   - **Yellow**: Used for another one-square piece, differentiating it from other single-square pieces.
   - **Gray**: Represents clear (empty) positions on the grid. This neutral color signifies availability for movement or occupation by a piece.

3. **Bold Edges**:
   - The bold outer edges of each piece (not the grid cells) emphasize the boundaries of the piece, making it visually distinct and easier to identify.

4. **Text Labels**:
   - Each piece and grid cell has a text label indicating its identifier (e.g., "rightl0", "square1"). This ensures that the viewer can easily associate the visual representation with its description.
   - The status of each object (e.g., "occupied", "clear") is also indicated within the shape to provide immediate context about its current state.

5. **Legend**:
   - A legend is included to map colors to their meanings (e.g., blue for "L" shaped pieces, gray for clear positions). This ensures that viewers unfamiliar with the color coding can understand the diagram.

6. **Contrast and Readability**:
   - High contrast between text and background colors is maintained to ensure that all labels and statuses are easily readable.
   - Text is placed strategically to avoid overlap and maximize the use of space, ensuring clarity and accessibility of information.

By using these visual elements consistently, the diagram effectively communicates the initial state of the Tetris puzzle, allowing viewers to understand the arrangement, status, and identity of each piece and grid cell.