image_speed = 0

switch current_month
{
case 1:  image_index = 0 break
case 2:  image_index = 1 break
case 3:  image_index = 2 break
case 4:  image_index = 3 break
case 5:  image_index = 4 break
case 6:  image_index = 5 break
case 7:  image_index = 6 break
case 8:  image_index = 7 break
case 9:  image_index = 8 break
case 10: image_index = 9 break
case 11: image_index = 10 break
case 12: image_index = 11 break
}

image_single = current_month - 1;