做旧信纸，咖啡渍刚刚好

A landscape-format 16:9 digital painting renders an old paper sheet as a background, the canvas framed horizontally so the paper fills the entire frame, its edges meeting the long sides while top and bottom crop precisely at the aspect-ratio boundary. The central area stays mostly clear for overlay text, occupying the middle third horizontally with a slightly warmer cast toward center-left for natural reading flow. Deckled, torn edges run along the left and right thirds; a pronounced diagonal crease cuts from lower-left to upper-right; clustered foxing spots gather in the upper-right quadrant, complemented by faint coffee stains lower-left. The surface carries fibrous paper grain, soft embossed fibers, and tiny pulp flecks, with selective ink bleed and feathered edges softening the stains. Lighting stays soft and even across the plane, revealing shallow relief and subtle shadow within the creases without any directional highlight. Render it as a tactile digital painting, adding subtle scanner-style noise and paper-fiber brushwork for an authentic aged character.