diff --git a/chapter18.playground/Contents.swift b/ch18/chapter18.playground/Contents.swift
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rename from chapter18.playground/Contents.swift
rename to ch18/chapter18.playground/Contents.swift
diff --git a/chapter18.playground/Sources/MetalView.swift b/ch18/chapter18.playground/Sources/MetalView.swift
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diff --git a/chapter18.playground/contents.xcplayground b/ch18/chapter18.playground/contents.xcplayground
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diff --git a/chapter18.playground/playground.xcworkspace/contents.xcworkspacedata b/ch18/chapter18.playground/playground.xcworkspace/contents.xcworkspacedata
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diff --git a/chapter18.playground/playground.xcworkspace/xcuserdata/marius.xcuserdatad/UserInterfaceState.xcuserstate b/ch18/chapter18.playground/playground.xcworkspace/xcuserdata/marius.xcuserdatad/UserInterfaceState.xcuserstate
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rename from chapter18.playground/playground.xcworkspace/xcuserdata/marius.xcuserdatad/UserInterfaceState.xcuserstate
rename to ch18/chapter18.playground/playground.xcworkspace/xcuserdata/marius.xcuserdatad/UserInterfaceState.xcuserstate
diff --git a/chapter18.playground/timeline.xctimeline b/ch18/chapter18.playground/timeline.xctimeline
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