The source code to this game was published not too long ago: https://github.com/TerryCavanagh/vvvvvv
Not under a free license but it's actually still being worked on there, with community involvement.
11 years after initial release that is quite impressive. (For any software project really, but especially for an indie game.)
Next version should be out soon it ssems: https://github.com/TerryCavanagh/VVVVVV/issues/267
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