I'm very very new to all this so I hope this is a good question.

I've heard about Hammer editor for Half Life 2 and watched Steve Lee's youtube videos regarding it. He stated that it's the best program to use for level design.

What if your level design is unlike what you're use to playing or making? I want to make a FPS RPG game (2d model in 3d environment).

The level design I'm after have the player rely heavily on one tool. The player level up by using said tool and can be modified and upgraded. This is how the player levels up.

What program do I use to create something that resembles this? Because it doesn't look like anything I can implement using half life 2 Hammer editor.