1.   But critics of the proposed flat tax contend that its simplicity masks a host of potential pitfalls for average taxpayers.

2.   Over the years, I have interviewed him a dozen times and concluded that his up-front California simplicity masks a complex, often anguished personality.

3.   Simplicity masks complexity.

4.   All this supposed simplicity surely masks the tremendous complexities behind the processing of data and transactions within a store.