Step 1: Start!
Open up the website
This website will give you a basic HTML5 asteroids game, no gimmicks or tricks, completely free.
Step 2: Download!
On the right side of the screen you should see a download zip button. Click it, and choose the designated place you wish for it to be downloaded at.
Step 3: Getting File Ready for Use.
Once you have downloaded the file you want to right click it and click extract all. From here you again select the location you wish for the file to be.
Step 4: Editor
Step 5: Once Downloaded
Once Brackets is downloaded open your extracted Asteroids game file. You will see a Game.js file. Once you see it you want to click open with, and then select brackets.
Step 6: Start Editing
Once game.js is open you are ready to start editing the most preliminary parts if the game. I recommend start with lines 368-379, as these are how the ship looks and are easy to notice differences once edited.
Step 7: See Your Work
To see your work at any given time go to top left of the screen, click file then save. Once you have saved your work open a new brackets file named index. On the right of the screen you should see a lighting bolt, double click this, and a new window will open up with the Asteroids game including YOUR edits!
Step 8: Done!
You can continue this process over and over again until you customize the game to be completely unique to yourself, and from here you are ready to edit or create more complex games.