In the 1960s, although the focus of world tank building had shifted to designing main battle tanks, development of heavy tanks continued. One example was the Czechoslovakian Vz. 63 Palcát («Mace»). The design stipulated ultimate protection and high firepower, as well as a connectable gun loading mechanism that required improved turret ventilation for extracting combustion gases. Difficulty to implement (large resource expenditure, long development, and major reconstruction of the production base) as well as the twilight of the heavy tank era led to the project's closure.