When I come up with stuff I don't really do it from a writers perspective. I start off using storyboards for everything I want to do instead of writing out what is going to happen. I usually do my storyboards on an actual story board on my wall, but I had to take it down for a while, so I use regular paper to create mini-story boards.
After that I come up with designs focusing around the theme for the specific scene, just sketching out random content and seeing what sticks is probably my favorite part. Because for one scene I will have about 60 different things to choose from and usually use only 4 to 5 pieces.
I came up during the end game you ride on a giant robot's arm that is themed after a highway. It's still a work in progress but I try to make it accurate to the concept. what in theory is suppose to happen is you shoot riders using the mouse when they appear or get too close. and bigger vehicles appear throwing out enemies that you also have to shoot that progressively gets more difficult. Iwould like it to have the boss slowly pan in the background as you progress across the highway(arm) I figure if it's coded correctly could be incredibly fun. it's just a simple mini-game masked with a bunch of content happening at the same time to give the illusion that it's really good. that's all games really are, masked with over the top things happening while the core gameplay is simple. you can do plenty of things with push "A" or move "up and down" but people are too stupid and not clever enough to figure that out.
I've been toying with the battle layout of the game too. This is what I've come up with so far. It's really rough and it doesn't have much yet. I want a major focus on the ability to use cards that are randomly generated by the enemy and player so I am for sure going to keep the card shuffle on their respective sides, but as you can see i have no space for hp for the 3 characters. I think at the top instead of enemy cards i will display their hp and it will change depending on which enemy you select to attack. I also don't like the character sprites. It's just, really traditional looking, and it doesn't seem that fun at all. If I could somehow make it so the camera enhances the screen to give it a closeup shot when they go and attack I think that would make it 100 times better.
I am in freaking love with sharpies!