+
+ // if we're on ice slow down acceleration or deceleration
+ if (isice(base.x, base.y + base.height))
+ {
+ /* the acceleration/deceleration rate on ice is inversely proportional to
+ * the current velocity.
+ */
+
+ // increasing 1 will increase acceleration/deceleration rate
+ // decreasing 1 will decrease acceleration/deceleration rate
+ // must stay above zero, though
+ if (ax != 0) ax *= 1 / fabs(vx);
+ }
+