The "penta prism hump" houses the 5 Axis IBIS... one of Olympus' new creative features, and keeps them leaps ahead of the Fuji "rangefinder" wannabe's.
Creativity, another attribute that has stood Olympus well since the middle of the 1900's, with camera's like the Olympus 6 folder, the OM series, the Olympus XA, the first mirrorless digital, and currently the OMD (EM5) and the EM1.😀