A smartphone case for holding and protecting a smartphone, while also having various features for controlling an app, such as a video game running on the smartphone. The smartphone case includes a case body having a case back, and a case side wall that extends circumferentially around the case back, including four corners. The case side wall also extends above and below a smartphone held by the case, thereby forming a front rim and a back rim. The case side wall also includes corner connectors configured to connect with a swappable input control module. The case back also includes dedicated controls, and at least one recess for storing a swappable control module while not in use. A long side of the case side wall includes a left bumper and a right bumper. An app provides a GUI for assigning the dedicated and swappable controls for an app to be controlled.