They're the standard keys for navigation in most shooters. Now see if you can make words using only the W, A, S, and D letters. You may use them multiple times if you so wish, but it may only build one unique word.
"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram
"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram