vallenzzz/beginner-tutorial ? reverse-engineered prompt

Build me a cute little pop up webpage that changes images when I click a button.

I want it to open as a stylized window with a background image, a heading, and an image area that starts on the first picture automatically. Each click on the button should fade out the current image, switch to the next one, then fade it back in smoothly. When it gets to the last image, the button should disappear and a final message should show instead.

Please make it easy to customize the colors, fonts, text, background, and image sequence, so I can swap in my own artwork later. I also want it to be mobile friendly and include decorative close and shrink icons in the design, even if they do not do much yet. Use plain HTML, CSS, and JavaScript, and keep the code simple enough that I can understand and edit it. If you need anything unclear, look up current docs online first.