Gallery title names replace '_' in the folder name with ' ' (generate_main_html()). To match against these title names when searching, we must also replace '_' with ' ' for each folder name we add to the list of titles to unhide.
In conjunction with styles.css change, changed W, and S keys to scroll image vertically and removed page change from Up and Down, leaving A, D, Left, and Right as keys for changing page. Page returns to the top when changing page. W and S scroll behavior is not smooth. Up and Down scroll relies on browser's in-built keyboard scrolling functionality.
Bodged file edit. Changed image to extend off the screen, and be scrollable. Easier to read speech and other text on smaller displays. Moved page counter to top center. Not quite as nice looking.
* More modern and efficient code, particularily for the JS
* Also the layout is better, with flexboxes and all
* The CSS and JS have their own files
* The sidebar has proper margins around the images
* You can use A + D and the arrow keys to navigate images, like on nhentai
* Images with a lot of width are properly sized
* There is a page counter on the bottom left