The horizontal scrolling system (see picture) is nice but can be improved.
Current drawbacks:
the left/right arrow is quite small, can be bigger
when pressing left/right arrow shows half of the video thumbnail (instead of full displaying it fully),
navigation requires patience, unnecessarily, because each click only adds one video (started from 16th and tried to reach 1st video, and was a bit tedious). The arrow can be set to move more videos when it is pressed once. Note: Actually there is a mechanism to move through more videos, but is quite random (if pressing some of the inner videos it moves more of them) and did not quite managed to grasp it
the Play arrow which shows up when hovering over the videos' thumbnails one would expect to play the videos. However it does nothing when pressing it. Instead one should click the other big Play arrow. It is counter intuitive. Initial expectation was that videos would be played when simply pressing the thumbnail
the Back button sends you to previous video. If one wants to go back to the Summary page (with all categories), then he may have a long way to go. It would be good to have a button 'Back to previous video', and another button 'Back to Summary'
Nice to have: to be able to swipe through videos by draging the mouse (or even better when just hovering the mouse towards the right or left of the page), then select any of the displayed videos with a single click on the video thumbnail, and play with double click.