Spice is a Zig library for low-overhead parallelism using heartbeat scheduling. It provides a fork/join model where workers maintain local work queues and a heartbeat thread periodically signals workers to offload work to others. The design avoids common work-stealing pitfalls: dynamic dispatch is minimized by using static calls for local work, queues are truly local (no atomics for push/pop in common case), and spinning is eliminated by using blocking waits. The library is demonstrated with a binary tree sum benchmark showing sub-nanosecond overhead. While primarily a research project with noted limitations (lack of tests, no array support), the implementation exhibits high craftsmanship in its concurrency primitives and performance optimizations.