Extensive air shower simulations : successes and challenges

Monte Carlo Simulations of extensive air showers are an essential foundation of many experimental projects in Astroparticle Physics, be it in imaging atmospheric Cherenkov telescopes, particle detector arrays measuring cosmic rays, or radio detectors for high-energy cosmic rays and neutrinos. The CORSIKA code in particular has shaped the field for over 20 years, yet new challenges arising in ever-more complex detectors are increasingly driving it to its limits. In this talk, I will review the successes and relevance of air-shower simulations, discuss open issues (such as the "muon puzzle") and current limitations, before describing how the independent re-implementation of air-shower simulation functionality in the modern CORSIKA 8 framework will allow us to tackle new challenges as well as profit from new results from particle physics experiments.