mirror of
https://github.com/italicsjenga/gba.git
synced 2024-12-27 12:41:30 +11:00
23 lines
1.2 KiB
Markdown
23 lines
1.2 KiB
Markdown
# Ch 2: User Input
|
|
|
|
It's all well and good to draw three pixels, but they don't do anything yet. We
|
|
want them to do something, and for that we need to get some input from the user.
|
|
|
|
The GBA, as I'm sure you know, has an arrow pad, A and B, L and R, Start and
|
|
Select. That's a little more than the NES/GB/CGB had, and a little less than the
|
|
SNES had. As you can guess, we get key state info from an IO register.
|
|
|
|
Also, we will need a way to keep the program from running "too fast". On a
|
|
modern computer or console you do this with vsync info from the GPU and Monitor,
|
|
and on the GBA we'll be using vsync info from an IO register that tracks what
|
|
the display hardware is doing.
|
|
|
|
As a way to apply our knowledge We'll make a simple "light cycle" game where
|
|
your dot leaves a trail behind them and you die if you go off the screen or if
|
|
you touch your own trail. We just make a copy of `hello2.rs` named
|
|
`light_cycle.rs` and then fill it in as we go through the chapter. Normally you
|
|
might not place the entire program into a single source file, particularly as it
|
|
grows over time, but since these are small examples it's much better to have
|
|
them be completely self contained than it is to have them be "properly
|
|
organized" for the long term.
|