Over normal terrain, infantry could move a maximum distance of eight squares, dragoons could move twelve squares, and light cavalry could move sixteen squares—intuitively mirroring the speed at which these units move in the real world. But terrain could impede movement: mountains were impassable, swamps slowed units down, rivers could only be crossed with the help of a special pontoon unit, etc. A player could only move one piece per turn, or one group of pieces if they were arranged in a rectangle. A piece could capture an enemy piece by moving into its square, just like in chess, but infantry and artillery pieces could also shoot enemy pieces, at a maximum ranges of two to three squares. Unlike chess, the pieces had orientation: for instance, an infantry piece could only shoot an enemy piece if they were facing it and flanking it. Hellwig's wargame could also simulate the fog of war to limited degree: while the players were arranging their pieces in their starting positions, they had the option of placing a screen across the board so that they could not observe their opponent's arrangement until the game started. Once the game was in progress, however, there was no hiding anything. Hellwig's wargame was a commercial success, and inspired other inventors to develop their own chess-like wargames. In 1796, another Prussian named Johann Georg Julius Venturini invented his own wargame, inspired by Hellwig's game. Venturini's game was played on an even larger grid. Venturini's game also added rules governing logistics, such as supply convoys and mobile bakeries, and the effects of weather and seasons, making this perhaps the first operational-level wargame. In 1806, an Austrian named Johann Ferdinand Opiz developed a wargame aimed at both civilian and military markets. Like Hellwig's game, it used a modular grid-based board. But unlike Hellwig's game, Opiz's game used dice rolls to simulate the unpredictability of real warfare. This innovation was controversial at the time. Hellwig, who designed his wargame for both leisure as well as instruction, felt that introducing chance would spoil the fun. A criticism of the chess-like wargames of Hellwig, Venturini, and Opiz was that the pieces were constrained to move across a grid in chess-like fashion. Only a single piece could occupy a square, even if that square represented a square mile; and the pieces had to move square by square, their exact location within a square being immaterial.