The revisiting of completed spaces is a common occurrence in videogames, as it allows assets to be reused. Bleszinski (2001b) uses the single term of backtracking to refer to these revisits, but the practise can be more precisely deconstructed into the two categories of backtracking and reversals. Backtracking consists occurs of level designs that the player has visited previously. Although this greatly saves development time, it can cause frustration, as players generally dislike the repetition of space (Ryan 1999a). Motive and variety, however, can be added through the addition of new devices, such as changes of time, new items to collect, new enemies to battle or new abilities to use in traversing the level. Reversal requires the player to travel from the end of the level to the start. This differs from back- tracking, where the player may revisit the space by beginning from the start. To function correctly, such spaces must have no bottlenecks or provide alternative routes to bypass bottlenecks. As with backtracking, a device is needed to motivate the player to re-conquer the land. Devices used in previous games include a timer that demands fast movement through the stage (as in Wario Land 4) or traps and enemies that function differently (as in Viewtiful Joe).