Building a Lego four-cylinder engine with acrylic sleeves is a fascinating project that combines creativity, engineering, and transparency for educational purposes. Acrylic sleeves, being clear, allow an unobstructed view of the engine’s moving parts, which is especially useful for demonstrating how pistons operate within cylinders. This visual transparency not only serves aesthetic appeal but also enhances understanding of internal combustion engine mechanics. When constructing such a model, attention to precision and fit is crucial to ensure smooth piston movement. Acrylic sleeves must be carefully cut and polished to reduce friction and avoid wear on Lego parts. Additionally, using Lego Technic components such as axles, gears, and connectors in conjunction with the acrylic sleeves can result in a functional demonstration of the four-stroke engine cycle. This version one of the Lego inline four-cylinder engine can serve as a stepping stone for enthusiasts interested in building more complex functional Lego engines or mechanical models. It also provides an excellent visual aid for teaching mechanical engineering basics, robotics, or steam punk style mechanical aesthetics. Moreover, the use of acrylic introduces an opportunity for customization—like adding colored transparent sleeves or integrating small LED lights to highlight movement. This approach encourages experimentation and deeper engagement with model building. Overall, projects like this highlight the joy of merging materials like acrylic with modular building systems such as Lego, expanding the possibilities for educational toys and demonstration tools.