Adjusting play based on stack sizes involves shifting your strategy to match the dynamics of deeper or shallower stacks. With a deep stack, there's more flexibility to play speculative hands and pursue larger pots, focusing on implied odds and post-flop play. Shallower stacks require a tighter, more aggressive approach, often prioritizing hands that have immediate strength, since there's less room for maneuvering post-flop. The goal is to maximize fold equity and reduce risk, particularly in tournaments where stack preservation is key. Understanding how stack depth impacts risk and reward is essential to adapting your strategy effectively.