There are 6 shapes on a 4x4 grid. Which shape is closest to the red 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: red right_triangle at (0, 1)
Distance from target shape to pink right_triangle at (3, 2): 4
Distance from target shape to yellow rectangle at (3, 0): 4
Distance from target shape to gray trapezoid at (2, 1): 2
Distance from target shape to purple right_triangle at (2, 3): 4
Distance from target shape to blue rectangle at (1, 0): 2
Closest shape is the gray trapezoid at (2, 1) with distance 2</think>

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