$X Off if cart is over $Y Shopify Script - https://dylanjh.com guides

gistfile1.txt

min_discount_order_amount = Money.new(cents:100) * 30
total = Input.cart.subtotal_price_was
discount = if total > min_discount_order_amount
              500
            else
              0
            end
message = "My message"

Input.cart.line_items.each do |line_item|
  product = line_item.variant.product
  next if product.gift_card?
  line_item.change_line_price(line_item.line_price - Money.new(cents: discount), message: message) unless discount == 0
end

Output.cart = Input.cart