if you prefer to develop this locally, you could first develop locally as a regular app,
Do you know of any IDE I can use (or even better may I know which IDE the Spark Core team uses) that supports the same toolchain as for the Spark Core “GNU Arm Embedded” https://launchpad.net/gcc-arm-embedded?
When doing everything in the Spark Core online IDE gives a lot of impracticalities: e.g.
a lot of tabs with all the different source code files,
when needing additional files doing the same iteration over and over again: add file locally -> push to GitHub -> import in online IDE …