Create an original vertical English flash-sale poster in deep red, black, and white, with a bold stacked headline, one angular discount band, and a compact coupon code strip. Text: “FRIDAY FLASH SALE”, “ONLY 48 HRS”, “UP TO 45% OFF”, “EXTRA 20% OFF”, “CODE: SAVE”. Use sparse light streaks and two small highlight stars only. No brand, watermark, QR code, website, non-English text, or random tiny text.