ball, map: Convert to left-hand rule

The SDL coordinate system has a negative orientation (the positive
y-axis points down).  It's easier to not fight it.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/ball.c b/src/ball.c
index 3230628..ccdccec 100644
--- a/src/ball.c
+++ b/src/ball.c
@@ -59,7 +59,7 @@ db_ball_new(int x, int y, int r, int a, int d, int sr, double s,
 		ball->cx = x;
 		ball->cy = y;
 		ball->x  = x + cos(a * (M_PI / 180)) * sr;
-		ball->y  = y - sin(a * (M_PI / 180)) * sr;
+		ball->y  = y + sin(a * (M_PI / 180)) * sr;
 	}
 	ball->r        = r;
 	ball->a        = a;
@@ -81,11 +81,11 @@ db_balls_move(struct db_ball *ball)
 {
 	if (ball->sr == 0) {
 		ball->x += cos(ball->a * (M_PI / 180));
-		ball->y -= sin(ball->a * (M_PI / 180));
+		ball->y += sin(ball->a * (M_PI / 180));
 	} else {
 		ball->a += ball->d * ball->s;
 		ball->x  = ball->cx + cos(ball->a * (M_PI / 180)) * ball->sr;
-		ball->y  = ball->cy - sin(ball->a * (M_PI / 180)) * ball->sr;
+		ball->y  = ball->cy + sin(ball->a * (M_PI / 180)) * ball->sr;
 		db_dbg("Spinning ball angle %f (speed %f, direction %d)",
 				ball->a, ball->s, ball->d);
 	}