Submarine in an Underground Neon City

A bold, line-art comic-book style illustration of a retro-futuristic submarine gliding through an expansive underground city. Carved into living rock, the cavern is lit by glowing neon crystals, glass tunnels, and suspended bridges. The submarine features a riveted steel hull, a tall periscope, a rotating propeller, and a bright searchlight cutting through mist. Dynamic perspective from a low angle, thick black ink outlines, cross-hatching, and halftone textures. Panel-like composition with speed lines and explosive blocks of electric blue, magenta, and lime green against charcoal cave walls. The underground city above and around shows air domes, shimmering waterfalls, and neon signs. Mood: adventurous pulp sci-fi, cinematic.