Techniques, not templates

Seamless Marquee: Two Copies, Half a Slide

A marquee loops with no visible jump when the run is repeated twice and slid by exactly half the track: half the track is one whole copy, so at the end copy two stands where copy one started and the restart has nothing to show. Three details decide it. The travel has to be translateX(-50%), a percentage of the element being transformed, so it tracks the run's width on its own. The track needs width: max-content, or it wraps at the parent's width. And the spacing belongs to the items, not the track: a gap sits between the two copies as well as inside them, so a 34px track gap puts one copy 17px out of step, while padding-inline-end leaves the halves identical.