Mostly-online teaching experiences in circuits and systems (CAS) during 2020-2021 COVID-19 pandemic are presented. Three case studies are shared summarizing course details, tools and platforms, best practices and limitations across three universities representing different continents. The presented approaches attempt to address several limitations of passive online delivery of CAS courses via interactive simulations, formative assessments via interactive web content and slide-embedded polls, at-home labs with student acquired hardware and instructor-lead and student-centered activity based learning.