By replacing the opaque plastic "tray" inside the CD case with clear material, for example, Shindo has been able to utilize even that tiny space.

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The flat panel displays, which make kaleidoscopic colors when jabbed with a finger, contain liquid crystal sandwiched between layers of glass or plastic which becomes opaque with an electric current.

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The boxes are clear plastic and have an opaque lid with a slot in it and four locks.

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Such materials might include plastic or photovoltaic glass, which changes from transparent to opaque at the flick of a button.

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