# LINE 1
    pygame.draw.rect(screen,BLACK,(
    THICK_BORDER+CLUES_WIDTH*CELL_SIZE,
    0,
    GRID_WIDTH*CELL_SIZE+(GRID_WIDTH/5+1)*THICK_BORDER+(GRID_WIDTH/5*4)*THIN_BORDER,
    THICK_BORDER
    ))

    # LINES 2 + 3
    for y in range(GRID_HEIGHT+1):
        if y%5 == 0:
            pygame.draw.rect(screen,BLACK,(
                0,
                THICK_BORDER + CLUES_HEIGHT*CELL_SIZE + (y/5)*(THICK_BORDER+4*THIN_BORDER+5*CELL_SIZE),
                THICK_BORDER + CLUES_WIDTH*CELL_SIZE + GRID_WIDTH*CELL_SIZE + (GRID_WIDTH/5+1)*THICK_BORDER + (GRID_WIDTH/5*4)*THIN_BORDER,
                THICK_BORDER
            ))
        else:
            pygame.draw.rect(screen,BLACK,(
                0,
                THICK_BORDER + CLUES_HEIGHT*CELL_SIZE + (y//5+1)*THICK_BORDER + (y-1-y//5)*THIN_BORDER + (y*CELL_SIZE),
                THICK_BORDER + CLUES_WIDTH*CELL_SIZE + GRID_WIDTH*CELL_SIZE + (GRID_WIDTH/5+1)*THICK_BORDER + (GRID_WIDTH/5*4)*THIN_BORDER,
                THIN_BORDER
            ))

    # LINE 4
    pygame.draw.rect(screen,BLACK,(
        0,
        THICK_BORDER+CLUES_HEIGHT*CELL_SIZE,
        THICK_BORDER,
        GRID_HEIGHT*CELL_SIZE+(GRID_HEIGHT/5+1)*THICK_BORDER+(GRID_HEIGHT/5*4)*THIN_BORDER
    ))
    # LINES 5 + 6
    for x in range(GRID_WIDTH+1):
        if x%5 == 0:
            pygame.draw.rect(screen,BLACK,(
                THICK_BORDER+CLUES_WIDTH*CELL_SIZE+(x/5)*(THICK_BORDER+4*THIN_BORDER+5*CELL_SIZE),
                0,
                THICK_BORDER,
                THICK_BORDER + CLUES_HEIGHT*CELL_SIZE+(GRID_HEIGHT/5+1)*THICK_BORDER + (GRID_HEIGHT/5*4)*THIN_BORDER + GRID_HEIGHT*CELL_SIZE
            ))
        else:
            pygame.draw.rect(screen,BLACK,(
                THICK_BORDER+CLUES_WIDTH*CELL_SIZE+(x//5+1)*THICK_BORDER+(x-1-x//5)*THIN_BORDER + (x*CELL_SIZE),
                0,
                THIN_BORDER,
                THICK_BORDER + CLUES_HEIGHT*CELL_SIZE+(GRID_HEIGHT/5+1)*THICK_BORDER + (GRID_HEIGHT/5*4)*THIN_BORDER + GRID_HEIGHT*CELL_SIZE
            ))