In keeping in line with their KISS philosophy, the littleBits Arduino module does not offer (easy) access to the full range of analog and digital I/O options that can be found on regular Arduino boards like the Arduino Uno. As a matter of fact, the littleBits Arduino only provides 3 bitSnap inputs and 3 bitSnap outputs if you intend on staying entirely within the littleBits ecosystem. Another difference is that unlike regular Arduino boards, the littleBits version uses its micro USB port for programming only. Power for the module must be supplied via one of the bitSnap inputs.
If you want to use your own sensors or actuators and you don’t have a Perf Module or Proto Module, or if the bitSnap inputs (or outputs as the case may be) are all full, hope is not lost. littleBits recognized that many users would need more I/O and all it takes is a little bit (no pun intended) of soldering.