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23 lines
1.2 KiB
Markdown
23 lines
1.2 KiB
Markdown
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# Ch 2: User Input
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It's all well and good to draw three pixels, but they don't do anything yet. We
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want them to do something, and for that we need to get some input from the user.
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The GBA, as I'm sure you know, has an arrow pad, A and B, L and R, Start and
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Select. That's a little more than the NES/GB/CGB had, and a little less than the
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SNES had. As you can guess, we get key state info from an IO register.
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Also, we will need a way to keep the program from running "too fast". On a
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modern computer or console you do this with vsync info from the GPU and Monitor,
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and on the GBA we'll be using vsync info from an IO register that tracks what
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the display hardware is doing.
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As a way to apply our knowledge We'll make a simple "light cycle" game where
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your dot leaves a trail behind them and you die if you go off the screen or if
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you touch your own trail. We just make a copy of `hello2.rs` named
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`light_cycle.rs` and then fill it in as we go through the chapter. Normally you
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might not place the entire program into a single source file, particularly as it
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grows over time, but since these are small examples it's much better to have
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them be completely self contained than it is to have them be "properly
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organized" for the long term.
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