Tweak global variable names to use '_'

starfield_blind2/arm9/source/template.c

@@ -3,9 +3,14 @@
 	Starfield demo
 	- Simulate a horizontal scrolling starfield using a framebuffer (no background tiles or sprites)
 	- Stars are tracked as an array of Star
-	- We will do the logic and drawing during the Vblank period
+	- We will do the logic and drawing during the V_blank period
 	Bonus:
 	- Added ability to scroll from the left of the right of the screen
+	- Add key input to control horizontal scrolling direction/speed
+	- TO-DO: Add staged speed increases
+	- TO-DO: Add twinkling stars
+	- TO-DO: Add option for different sized stars
+	- TO-DO: Performance timing between memcpy vs DMA?
 
 ***/
 
@@ -17,8 +22,10 @@
 #define SPACE_COLOR		RGB15(0,0,0)	// black
 #define STAR_COLOR		RGB15(31,31,31)	// white
 
-// control flags
-#define SCROLL_RIGHT	0	// '0' - start at left of screen. '1' - start at right of screen
+enum {
+	SCROLL_RIGHT = 0,
+	SCROLL_LEFT
+};
 
 // our Star object
 typedef struct {
@@ -29,7 +36,9 @@ typedef struct {
 } Star;
 
 // our Stars
-Star stars[NUM_OF_STARS];
+Star _stars[NUM_OF_STARS];
+// scrolling state
+int _scroll_state = SCROLL_RIGHT;
 
 // wipe everything to make sure we're drawing on an empty screen
 void ClearScreen() {
@@ -45,10 +54,10 @@ void InitStars() {
 	int i;
 
 	for(i = 0; i < NUM_OF_STARS; i++) {
-		stars[i].x = rand() % SCREEN_WIDTH;
-		stars[i].y = rand() % SCREEN_HEIGHT;
-		stars[i].speed = (rand() % MAX_STAR_SPEED) + 1;	// because the range is 1-4. We don't want stars that are stopped
-		stars[i].color = STAR_COLOR;
+		_stars[i].x = rand() % SCREEN_WIDTH;
+		_stars[i].y = rand() % SCREEN_HEIGHT;
+		_stars[i].speed = (rand() % MAX_STAR_SPEED) + 1;	// because the range is 1-4. We don't want stars that are stopped
+		_stars[i].color = STAR_COLOR;
 	}
 }
 
@@ -58,14 +67,14 @@ void EraseStar(Star *star) {
 }
 
 void MoveStar(Star *star) {
-	if(SCROLL_RIGHT)
+	if(_scroll_state == SCROLL_RIGHT)
 		star->x += star->speed;
 	else
 		star->x -= star->speed;
 
 	// checks to see if it falls off screen. If it does, we create a new star
 	if(star->x > SCREEN_WIDTH) {
-		star->x = (SCROLL_RIGHT) ? 0 : SCREEN_WIDTH;
+		star->x = (_scroll_state == SCROLL_RIGHT) ? 0 : SCREEN_WIDTH;
 		star->y = rand() % SCREEN_HEIGHT;
 		star->speed = (rand() % MAX_STAR_SPEED) + 1;
 	}
@@ -94,10 +103,21 @@ int main() {
 
 	// do logic and drawing for our starfield during Vblank
 	while(1) {
+
+		// get the current state of our keys
+		scanKeys();
+
+		// control the scrolling with the d-pad
+		if(keysHeld() & KEY_LEFT)
+			_scroll_state = SCROLL_RIGHT;
+		else if(keysHeld() & KEY_RIGHT) 
+			_scroll_state = SCROLL_LEFT;
+
+		// do our drawing stuff
 		for(i = 0; i < SCREEN_WIDTH * SCREEN_HEIGHT; i++) {
-			EraseStar(&stars[i]);
-			MoveStar(&stars[i]);
-			DrawStar(&stars[i]);
+			EraseStar(&_stars[i]);
+			MoveStar(&_stars[i]);
+			DrawStar(&_stars[i]);
 		}
 
 		// make sure we pause for the whole VBlank period before we end