I don't think this game is all that representative of context-switching overhead, as my 4th attempt gives evidence that this improves quickly with practice:

    RT in pure trials: 422ms
    RT in mixed trials: 611ms
    Mixing cost: 189ms
    RT in task-repeat trials (in mixed blocks): 611ms
    RT in task-switching trials (in mixed blocks): 602ms
    Task-switch cost: -9ms

The "mixed trials" are naturally slower because I'm having to recognise 4 patterns instead of 2, but only by ~50%.