Selective opacity emerges when a syntactic constituent is transparent only to certainoperations. The Williams Cycle (Williams, 2003) derives opacity from structural size: Larger clauses are opaque to more syntactic operations than smaller clauses. This thesis demonstrates that Hungarian exhibits Williams Cycle effects extensively. Additionally, the opacity of Hungarian embedded clauses depends on their final position in the matrix clause: Clauses ending up higher are opaque to more operations. I provide a unified analysis for size- and position-dependent opacity by introducing a new constraint on movement. According to this, movement steps must start and end in the same extended projection. Lacking clause-edge positions usable as escape hatches, Hungarian embedded clauses must re-merge with an equal-sized matrix projection and find a continuation in the matrix clause to become transparent. From this, size-dependent opacity follows because larger clauses re-merge later; and position-dependent opacity follows because re-merged embedded clauses cannot leave their adjunction-sites.