sry, i forgot a speed_y = -speed_y;

while(1)
{
while (obj_pan.pos_x <= 500)
{
obj_pan.pos_x += speed_x;
wait(1);
}
obj_pan.pos_x = 500;
speed_x = -speed_x;
while(obj_pan.pos_y <= 500)
{
obj_pan.pos_y += speed_y;
waít(1);
}
obj_pan.pos_y = 500;
speed_y = -speed_y;
while(obj_pan.pos_x >= 300)
{
obj_pan.pos_x += speed_y;
wait(1);
}
obj_pan.pos_x = 300;
speed_x = -speed_x;
while(obj_pan.pos_y >= 300)
{
obj_pan.pos_y += speed_y;
wait(1);
}
obj_pan.pos_y = 300;
speed_y = -speed_y;
wait(1);
}