Fond Pixel Art pour Shoot 'Em Up

Vertical retro pixel-art scrolling background for a space shoot 'em up game, composed in a 9:16 portrait orientation. A deep black starfield filled with hundreds of tiny white, blue, and violet pixel stars, flanked by two luminous vertical nebula streams: electric purple and blue on the left, and purple with cyan highlights on the right. Exactly 3 visible celestial bodies: a large purple cratered planet near the upper left edge, a large blue-purple rim-lit planet partially cropped on the lower right edge, and a small purple moon beneath it. Exactly 22 irregular cratered gray-brown asteroids with cool purple shadows placed along the edges: 1 huge asteroid near the upper right, 1 medium asteroid at the middle right, 1 medium asteroid at the lower left, 2 large asteroids cropped at the bottom corners, and 17 smaller asteroids scattered along the borders. Composition keeps a wide, dark central vertical flight corridor completely open for gameplay. Crisp 16-bit pixel-art style with chunky jagged silhouettes, meticulous dithering, and vivid rim lighting. No ships, no player UI, no text, no watermarks, seamless game asset aesthetic.