InflatiBits is a modular construction kit that enables playful exploration of pneumatically actuated kinematic systems. The kit contains different building blocks based on soft robotics principles such as soft inflatable air-chambers, constraining elements, air-connectors, pressure sources, and sensor modules. The elements can be combined and actuated manually or through an optional Arduino-based control board. The board contains a motorized air-pump, solenoid valves and allows for connecting the sensor module to achieve more complex behaviors and motion patterns. The InflatiBits modules and connectors are compatible with standard Lego parts, enabling children to integrate them into existing playing environments.