Fix engine sound effects

2 files changed, 19 insertions, 6 deletions

diff --git a/TODO.org b/TODO.org
index c91d2af..d883a04 100644
--- a/TODO.org
+++ b/TODO.org
@@ -27,6 +27,6 @@
 ** TODO Reduce lanes to 3 from level 10
 *** TODO Handle vehicles lane change for reductions
 ** DONE Add music
-** STARTED Add sound effects
+** DONE Add sound effects
 ** TODO Draw sprites in batch for perf
 ** TODO Package as flatpack
diff --git a/turbo.scm b/turbo.scm
index 3bd3d99..d86598a 100644
--- a/turbo.scm
+++ b/turbo.scm
@@ -148,10 +148,25 @@
 (define (level-min-speed)
   (+ player-min-speed (* (- level-difficulty 1) 36)))
 
+(define car-gears 5)
+
+(define (gearing-range)
+  (/ (* 1.05 player-max-speed) car-gears))
+
+(define (speed->gear speed)
+  (let ((gear-range (gearing-range)))
+    (floor (/ speed gear-range))))
+
+(define (speed->engine-power speed)
+  (let* ((gear (speed->gear speed))
+	 (speed-range (* gear (gearing-range))))
+    (/ (- speed speed-range) speed-range)))
+
 (define (set-player-speed! new-speed)
   (let* ((min-speed (level-min-speed))
 	 (player-speed (max (min new-speed player-max-speed) min-speed))
-	 (pitch-factor (* 0.10 (- player-speed min-speed))))
+	 (engine-power (speed->engine-power player-speed))
+	 (pitch-factor (+ 1 engine-power)))
     (set-vehicle-speed! player-car player-speed)
     (set-source-pitch! engine-sound (+ 1 pitch-factor))))
 
@@ -208,7 +223,7 @@
 
 (set-source-volume! music 0.5)
 
-(source-play music)
+; (source-play music)
 (source-play engine-sound)
 
 (define (update interval)
@@ -230,9 +245,7 @@
 
     (let ((new-speed (+ (vehicle-speed player-car)
 			(* player-current-acceleration interval))))
-      (set-vehicle-speed! player-car (min player-max-speed
-					  (max (level-min-speed)
-					       new-speed))))
+      (set-player-speed! new-speed))
 
     (when (and game-started? (player-collides?))
       (off-road-player)