Prev: 6990 Up: Map Next: 6A45
6A3F: Calculate mirrored right edge position
For symmetric islands (state_island_byte_3=1). Right edge = 2*$3C - left = 120 - left. This mirrors the left edge around screen center, creating a symmetric island shape.
calc_mirrored_edge 6A3F LD A,C A = 2*C - D = 120 - left_x, then jump to draw_right_edge.
6A40 SUB D
6A41 ADD A,C
6A42 JP draw_right_edge
Prev: 6990 Up: Map Next: 6A45