There are 3 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, 3)
Distance from target shape to gray square at (2, 1): 3
Distance from target shape to pink right_triangle at (1, 0): 5
Closest shape is the gray square at (2, 1) with distance 3</think>

<answer>(2, 1)</answer>