Fix car sliding

TODO.txt

@@ -1,5 +1,6 @@
 =========== GENERAL ==============
 
+- car deglitch idea: deglitch only if the middle joint collided this frame?
 - some kinda easteregg in menu or smt
 - make the U-ramp map taller due to new physics
 - replay format should probably record game version

racing.h

@@ -1156,11 +1156,13 @@ uint32_t LCR_racingStep(unsigned int input)
     LCR_racing.carBody.joints[4].velocity[1],
     LCR_racing.carBody.joints[4].velocity[2]);
 
-  // apply gravity only if wheels are on the ground (prevents sliding a bit):
+  /* Apply gravity like this: if all wheels are on ground, we don't apply
+    gravity to roof. This helps prevent sliding. */
 
-  if (((LCR_racing.wheelCollisions | (LCR_racing.wheelCollisions >> 4))
-    & 0x0f) != 0x0f)
-    TPE_bodyApplyGravity(&(LCR_racing.carBody),LCR_GRAVITY);
+  for (i = 0; i < 5; ++i)
+    if (i < 4 || (((LCR_racing.wheelCollisions |
+      (LCR_racing.wheelCollisions >> 4)) & 0x0f) != 0x0f))
+      LCR_racing.carBody.joints[i].velocity[1] -= LCR_GRAVITY;
 
   if (LCR_racing.wheelCollisions) // at least one wheel on ground?
   {

tinyphysicsengine.h

@@ -2,6 +2,9 @@
 #define _TINYPHYSICSENGINE_H
 
 /**
+  NOTE: This is a Licar specific fork of the library. Changes made can be
+  found e.g. with diff.
+
   tinyphysicsengine (TPE)
 
   Simple/suckless header-only hybrid 3D physics engine with no floating point,
@@ -1038,7 +1041,9 @@ void TPE_worldStep(TPE_World *world)
 
         if (hard)
         {
-          TPE_bodyReshape(body,world->environmentFunction);
+         /* Licar modification: we only reshape if the tension requires it. This
+            prevents car from sliding when standing on ground. */
+      //    TPE_bodyReshape(body,world->environmentFunction);
 
           bodyTension /= body->connectionCount;