So, annoyingly, most JS solutions don't do horizontal tickers on an infinite loop, nor do they render all that smoothly.
The difficulty with CSS was getting the animation to transform the entire items 100% yet include an offset that was only the width of the browser (and not the items full width).
Setting the start of the animation to anything less than zero (e.g. -100%) is unreliable as it is based on the items width, and may not offset the full width of the browser or creates too large an offset
Padding left on the wrapper allows us the correct initial offset, but you still get a 'jump' as it then loops too soon. (The full text does not travel off-screen)
This is where adding display:inline-block to the item parent, where the natural behaviour of the element exists as inline, gives an opportunity to add padding-right 100% here. The padding is taken from the parent (as its treated as inline) which usefully is the wrapper width.
Magically* we now have perfect 100% offset, a true 100% translate (width of items) and enough padding in the element to ensure all items leave the screen before it repeats! (width of browser)
*Why this works: The inside of an inline-block is formatted as a block box, and the element itself is formatted as an atomic inline-level box. Uses `box-sizing: content-box`
Padding is calculated on the width of the containing box.
So as both the ticker and the items are formatted as nested inline, the padding must be calculated by the ticker wrap.
Simone Giertz STEM icon, Swedish inventor, robotics enthusiast, TV host, professional YouTuber, and passion-provoking educator