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

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