Creation of a computer game (especially FPS, popularly nicknamed "walker") requires from oneself not only huge time resources, knowledge of the basics of design and programming, but also an elementary sense of taste. However, a lot has already been invented before us, and borrowing some other people's achievements, you can create quite a good shooter-adventure.
Instructions
Step 1
Select an engine. Creating your own engine is so difficult that not every studio takes it up. For example, the instrument on which "Half-life 2" was created - "Source" was used in more than 50 games from different studios. However, programming directly with Source (as well as Unreal Engine (Gears of war), as well as CryEngine (Crysis)) requires several months of training. There are tools like "Garry's mod" for "Source" that can make the engine a lot easier - I'd recommend using them. Check out the FPS Creator as well.
Step 2
Think about the setting. Clearly "imagine the world" in which the events of your game will take place (be it the distant future or a city infected with a virus). Think over the storyline and the main characters that appear in it. Try not to overcomplicate the action, but also avoid missing a plot. Take "Bioshok" as an example, where the storytelling is an important part of the game.
Step 3
Determine the features of the gameplay. Something that will be able to "distinguish" your walker from hundreds of others. For example, "Portal" was popular because of the original concept, and "Half-Life" because of the constant variety - remember, the player was constantly placed in new situations and thrown in new enemies. On the other hand, games about which you can say "I've seen this somewhere before" are not so popular among people.
Step 4
Work on balance. It is very important that all the ideas you have conceived can be realized. For example, the developers of "Counter-Strike", although they made a very popular game, were mistaken in one thing: they incorrectly calculated the balance of the weapon, which is why the players do not use many "guns" at all. Therefore, it is in your best interest for all the contents of the future adventure game to work as you intended.
Step 5
Assemble a team. Your opinion, as the main developer, may and will be decisive, but constructive criticism is always necessary. What's more, other people can take on a significant load of maps, models, and general level design. Plus, this way you can brainstorm and end up with a much better product than what you would do alone.
