This chapter provides an overview of the current state of radar-based Human-Computer Interaction (HCI) and outlines future research directions. While earlier chapters in this book have explored specialised domains, such as through-material sensing, ambient intelligence, surface context awareness, hand air-writing, and on-object gesture detection, this chapter expands this perspective by examining fifty carefully selected publications that address a broad range of design and technical considerations in radar-based HCI. We review key design choices, including gesture set definitions, sensor placements, radar types, frequency ranges, signal representations, and classification algorithms. Building on this foundation, the chapter then presents a forward-looking discussion of research opportunities. Particular emphasis is placed on the need for miniaturised, energy-efficient, and adaptive radar systemsAdaptive radar systems capable of functioning reliably in diverse, real-world settings. Additionally, the chapter stresses the importance of developing open, standardised datasets to support reproducibility, improve generalizability, and promote inclusive design.