add examples 'tilt-sensor' (sensor reading on mobile devices)

examples/tilt-sensor/lisp/main.lisp

@@ -0,0 +1,57 @@
+(in-package :maze)
+
+(defconstant +w+ 13) ; ball width
+
+(defvar *x*)         ; ball x
+(defvar *y*)         ; ball y
+
+(defun move (x-rotation y-rotation) ; called from QML
+  (labels ((add (x)
+             (truncate (signum x)))
+           (to-pos (x)
+             (truncate (/ (+ x (/ +w+ 2))
+                          +w+)))
+           (normalize (x)
+             (* (to-pos x) +w+)))
+    (let* ((dx (min (* 0.2 x-rotation) (1- +w+)))
+           (dy (min (* 0.2 y-rotation) (1- +w+)))
+           (add-x (add dx))
+           (add-y (add dy)))
+      (if (aref *maze*
+                (+ add-x (to-pos *x*))
+                (to-pos *y*))
+          (setf *x* (normalize *x*))
+          (incf *x* dx))
+      (if (aref *maze*
+                (to-pos *x*)
+                (+ add-y (to-pos *y*)))
+          (setf *y* (normalize *y*))
+          (incf *y* dy))))
+  (move-ball)
+  (values))
+
+(defun move-ball ()
+  (if (and (= *x* +w+)
+           (= *y* 0))
+      (new-game)
+      (let ((ball (find-quick-item ui:*ball*)))
+        ;; 'qset' is faster than 'q>', but can't trigger animations
+        (qset ball |x| (- *x* 0.5))
+        (qset ball |y| (- *y* 0.5)))))
+
+(defun start ()
+  (setf *x* (* +w+ (- *width*  1))
+        *y* (* +w+ (- *height* 2)))
+  (move-ball)
+  (q> |running| ui:*timer* t))
+
+(defun stop ()
+  (q> |running| ui:*timer* nil))
+
+(defun new-game ()
+  (new-maze)
+  (start))
+
+(progn
+  (start)
+  (qlater 'ini))