Mauville is an exciting city containing many of the key buildings found in all regions. It holds Hoenn's bike shop as well as the game corner. Most importantly, the Mauville City Gym is located here, which is where you'll obtain your third gym badge. The city also has the usual amenities like the Pokémon Center and the Poké Mart. The Poké Mart conveniently sells Paralyz Heals for the price of a Poké Ball, which will come in handy against the powerful Electric-types in the Mauville City Gym.
There is an old man in the house next to the doorless yellow building that will give you HM06 Rock Smash. It is a decent Fighting-type move in battle, but its main use is outside of battle, letting you destroy certain rocks and clearing passageways. If you go behind the fence opposite the Poké Mart you can find an X Speed.
Here you are given your very own bike! You are given the option of taking the Acro Bike and the Mach Bike. The Acro bike is slower, but has better acceleration and is easier to turn. Your choice does not make a major difference, as you can exchange bikes at any time. However, each bike allows certain places to be accessible.
Mauville Game Corner
The Mauville Game corner has lots of TMs. This Game Corner has Psychic, Flamethrower, Ice Beam and Thunderbolt!
This is the only Game Corner in Pokémon Ruby and Sapphire. There is another Game Corner in Mossdeep City for Emerald users.
In order to play at the Game Corner, you first must acquire a Coin Case. Talk to the lady in the house beside the Poké Mart. She will mention Harbor Mail, which needs to be bought in Slateport City. If you didn't buy it or obtain it at the Trick House's second puzzle, you can take the bike route there and back. The Harbor Mail may be exchanged for the Coin Case.
The Game Corner has two games - slot machine (with a chance of a high payout), or roulette (which has a slow but steady payout.)
Mauville City Gym
This Gym specializes in Electric types. It is recommended that you bring a Rock Type Pokémon like Geodude which can be found in Granite Cave in Dewford Town.
Wattson can be the first major challenge for many trainers. His Pokemon will electrocute Flying and Water types, and his Magnemite and Magneton will resist most forms of damage. To top things off, Voltorb is a powerful speedster, with Sonicboom and Selfdestruct threatening to deal relatively major damage.
A ground type Pokemon like Geodude will be immune to dangerous electric attacks, although it will still have worries thanks to the sheer power of Wattson's attacks. If you picked Torchic to start with or have gotten yourself a Pokemon with Fighting moves, you will be glad to hear that Magnemite and Magneton are weak against Fire and Fighting attacks.
Beating Wattson wins you TM34, which is Shockwave. He will also give you your third gym badge, the Dynamo Badge. It will boost the speed of all your Pokémon as well as allow you to use Rock Smash outside of battle, letting you complete the route between Pokémon Ruby and Sapphire/Verdanturf Town and continue north along Route 111.
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