We extend live sequence charts (LSCs), a highly expressive variant of sequence diagrams, with timing constructs, thus making the language suitable for specifying the behavioral requirements of time-intensive systems. We follow Alur and Henzinger in basing the extension on a single clock object. We have implemented the extension in full in our play-engine tool, which provides user-friendly ways to play in the timing constraints, together with a powerful mechanism that can execute, or play out, the time-enriched requirements directly, without the need for an intra-object system model. It seems that in addition to many advantages in testing and requirements engineering, for some kinds of systems this could lead to the requirements actually serving as the final implementation.