that sneaks up on the viewer , providing an experience that is richer than anticipated 
(ROOT (S (NP (DT that)) (VP (VBZ sneaks) (PRT (RP up)) (PP (IN on) (NP (DT the) (NN viewer))) (, ,) (S (VP (VBG providing) (NP (NP (DT an) (NN experience)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (ADJP (ADJP (JJR richer)) (SBAR (IN than) (S (VP (VBN anticipated))))))))))))))
(ROOT (S (NP (DT )) (VP (VBZ ) (PRT (RP )) (PP (IN ) (NP (DT ) (NN ))) (, ) (S (VP (VBG ) (NP (NP (DT ) (NN )) (SBAR (WHNP (WDT )) (S (VP (VBZ ) (ADJP (ADJP (JJR )) (SBAR (IN ) (S (VP (VBN ))))))))))))))