Coding can be done in C-style language with the Arduino IDE.
Bittle X/ Bittle / Nybble can be programmed with a Scratch-like IDE Mind+. we also provide a free sample curriculum.
Bittle can be programmed with a Scratch-like web-based IDE Codecraft. You may find some complementary materials: online help and curriculum.
Note that Codecraft doesn't support OpenCat 2.0. You'd need to use OpenCat 1.0 instead.
OpenCatWeb - a web interface to control Opencat-based robots
need to mount a Raspberry Pi
a discussion thread by the author leukipp
The Code & Robots iOS app can control a few open source Robots, including Bittle.
Please check out the following video for the app configuration to support controlling Bittle.