A method of controlling combustion in an homogenous charge compression ignition engine through indirect mechanisms. The compact computing system can take the form of a desktop computer. The housing provides a first exemplary engaginglocking feature including an orthogonal tongue and a groove that receives the tongue, and a second exemplary engaginglocking feature that includes a groove having an intermittently varying cross-sectional area and that retains a gasket of constant cross-sectional area.