This project examines level design strategies across three casual puzzle games- Garden Tails, A Froggo Story, and Tile Rush, to understand how challenge pacing, mechanic layering, and progression influence player experience. Conducted during a six-month internship at Zynga, the project involved hands-on design work across different gameplay philosophies. Garden Tails emphasised emotional storytelling and layered mechanics, Froggo focused on player discovery and FTUE alignment, while Tile Rush prioritised fast decision-making and spatial strategy. Over 370 levels were designed across the three games, supported by structured playtesting and clear documentation systems. A custom level-solving bot was developed to test solvability, calibrate difficulty, and simulate varied player behaviours, helping identify issues early in the design process. The project resulted in a practical, player-centered approach to puzzle level design that balances cognitive challenge with engaging and memorable gameplay.