Swarm behaviour engineering is inherently challenging due to the need for agents to coordinate based on local interactions. This paper introduces MacroSwarm, a Scala-based aggregate programming framework that supports design of swarm behaviors via composable, high-level building blocks. These include primitives for tasks like aggregation, flocking, and collective decision-making. Based on field-based coordination, MacroSwarm enables expressive and reusable behavior modeling, ideal for large-scale, decentralized swarm systems.