mobility in the upright state. The SRiMech is typically an electric or pneumatic arm or extension on the upper surface of the robot which pushes against the arena floor to roll or flip the robot upright. Most flippers, some lifters, and even some carefully designed axes can double as SRiMechs. Even a vertical spinning weapon may be used as a crude self-righting device. Team Nightmare's lightweight vertical spinner Backlash was designed such that when flipped it would hit the ground with the spinning disc and kick back upright. The first successful unaided use of an SRiMech in competition was at the 1997 U.S. Robot Wars when the immobilized Vlad the Impaler used a dedicated pneumatic device to pop back upright in a match against Biohazard. Many modern rulesets, such as the rebooted versions of BattleBots and Robot Wars, require robots to have an active weapon in order to improve the visual spectacle, thus eliminating certain designs such as torque-reaction axlebots and thwackbots, and requiring other designs such as wedges and rammers to incorporate some other kind of weapon. Interchangeable weaponry It is increasingly common for robots to have interchangeable weaponry or other modular components, allowing them to adapt to a wide range of opponents and increasing their versatility; such robots are often referred to as "Swiss army bots", in reference to Swiss army knives. Arguably the earliest example was Robot Wars Series 1 contestant Plunderbird, which could change between a pneumatic spike and a circular saw on an extendable arm. Successful Swiss army bots include Robot Wars Series 6 champion Tornado, BattleBots 2016 runner-up Bombshell, and top-ranked US Beetleweight Silent Spring. Sometimes, robots that were not originally Swiss army bots have had their weapons changed or altered on the fly, typically due to malfunctions. In BattleBots 2015, Ghost Raptors spinning bar weapon broke in its first fight; builder Chuck Pitzer then improvised new weapons for each following fight, including a "De-Icer" arm attachment which it used to unbalance and defeat bar spinner Icewave in the quarter-finals. Prohibited weaponry Since the first robot combat competitions, some types of weapons have been prohibited either because they violated the spirit of the competition or they could not be safely used. Prohibited weapons have generally included: Radio jamming High voltage electric discharge Liquids (glue, oil, water, corrosives...) Fire (except in BattleBots and Norwalk Havoc) Explosives Un-tethered projectiles (except in BattleBots from 2018 season onwards)