Build an image gallery with lightbox

• A responsive grid of thumbnails (CSS grid, columns adapting to the width) with captions or alt text
• Clicking a thumbnail opens a lightbox overlay with the large image, caption and counter ("3 / 12")
• Previous and Next buttons, the left and right arrow keys, and Escape (or clicking the backdrop) close and navigate; navigation wraps around or stops at the ends, consistently
• Thumbnails use loading="lazy", the lightbox preloads the neighbouring images, and a placeholder or spinner shows while the large image loads
• Focus is trapped in the lightbox while open, body scrolling is locked, and focus returns to the thumbnail that opened it on close
• The overlay has role="dialog", aria-modal="true" and a label, and image loading errors show a fallback

Only after every requirement works.

• Swipe gestures on touch devices
• Zoom and pan on the large image
• URL hash sync so a specific image can be linked