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Excellent design & workmanship! You're a gifted young man indeed!
Great idea! (Just like a signal mirror!) So if you lose your signal mirror but have a CD (or intentionally take one with you--good idea!) you can still readily signal aircraft, etc.
He's applauding your comment about what you LIKE in the Instructables community. You wrote a valuable Instructable, then applauded those who added beneficial information to it by giving the benefit of their own experience. Good job!