There are 6 shapes on a 4x4 grid. Which shape is closest to the purple right_triangle in terms of Manhattan distance? The final answer is the grid position of the closest shape like (row_index, column_index).
<think>Target shape: purple right_triangle at (3, 1)
Distance from target shape to blue rectangle at (3, 0): 1
Distance from target shape to orange square at (3, 3): 2
Distance from target shape to red right_triangle at (3, 2): 1
Distance from target shape to gray rectangle at (1, 0): 3
Distance from target shape to brown rectangle at (1, 1): 2
Closest shape is the blue rectangle at (3, 0) with distance 1</think>

<answer>(3, 0)</answer>