Here's why and how to get through:
Why you can't just walk through:
* Rock-type Pokemon: The Rock Tunnel is filled with strong Rock-type Pokemon, such as Geodude, Onix, and Graveler. These are very tough to defeat with the Pokemon you'll have at this stage of the game.
* Darkness: It's dark inside the tunnel, making it harder to see and fight effectively.
How to get through:
1. Obtain Flash: You need the Flash HM (Hidden Machine) to illuminate the tunnel. You can get Flash by speaking to the old man in the house just north of the entrance to the Rock Tunnel in Vermilion City.
2. Get a Pokemon that can learn Flash: The Pokemon you need will vary, but common choices include:
* Pikachu: It can learn Flash by leveling up.
* Squirtle: It can learn Flash from a TM (Technical Machine).
3. Use Flash: Once you've got Flash, use it inside the tunnel to clear the darkness. This will make it easier to see and fight.
Tips:
* Prepare for Rock-type Pokemon: Bring Pokemon that are strong against Rock-type Pokemon, such as Water, Grass, Fighting, Ground, and Steel types.
* Stock up on Potions: You'll need lots of healing items to keep your Pokemon in top shape.
* Be patient: The Rock Tunnel can be challenging, so don't be discouraged if you need a few tries to get through.
Once you make it through the Rock Tunnel, you'll be rewarded with the chance to catch a rare Pokemon, like a Machop or a Graveler!