diff --git a/balls.cc b/balls.cc
index fc9d25b..a514d1b 100644
--- a/balls.cc
+++ b/balls.cc
@@ -1,6 +1,6 @@
-#include <stdlib.h>
-#include <math.h>
-#include <assert.h>
+#include <vector>
+#include <cmath>
+#include <cassert>
 
 #include "game.h"
 #include "balls.h"
@@ -15,10 +15,10 @@ unsigned int v_min = 0;
 unsigned int v_angle_min = 0;
 unsigned int v_angle_max = 100;
 
-struct ball * balls = 0;
+ball * balls = nullptr;
 unsigned int n_balls = 50;
 
-static void random_velocity(struct ball * p) {
+static void random_velocity(ball * p) {
     double r2;
     do {
 	p->v_x = v_min + rand() % (v_max + 1 - v_min);
@@ -47,7 +47,7 @@ void balls_init_state () {
     }
 }
 
-void ball_update_state (struct ball * p) {
+void ball_update_state (ball * p) {
     struct gravity_vector g;
     gravity_get_vector (&g, p);
 
@@ -87,7 +87,7 @@ void ball_update_state (struct ball * p) {
 	p->angle += 2*M_PI;
 }
 
-void ball_elastic_collision (struct ball * p, struct ball * q) {
+void ball_elastic_collision (ball * p, ball * q) {
     double dx = q->x - p->x;
     double dy = q->y - p->y;
     double d2 = dx*dx + dy*dy;
@@ -112,7 +112,7 @@ void ball_elastic_collision (struct ball * p, struct ball * q) {
     }
 }
 
-void ball_reposition (struct ball * b) {
+void ball_reposition (ball * b) {
     if (b->x < b->radius)
 	b->x = b->radius;
     else if (b->x + b->radius > width)
@@ -128,38 +128,35 @@ int face_rotation = 0;
 
 static const double linear_rotation_unit = 2.0;
 
-static unsigned int faces_count;
-static struct ball_face ** faces;
+static std::vector<ball_face *> faces;
 
-struct ball_face {
+class ball_face {
+public:
+    ball_face (unsigned int radius, cairo_surface_t * face, int rotation);
+    ~ball_face ();
+    cairo_surface_t * get_surface (double angle) const;
+private:
     unsigned int rotations;
-    cairo_surface_t ** c_faces;
+    std::vector <cairo_surface_t *> c_faces;
 };
 
 static double random_color_component() {
     return 1.0*(rand() % 200 + 56)/255;
 };
 
-static struct ball_face * new_ball_face(unsigned int radius, cairo_surface_t * face, int rotation) {
-    struct ball_face * f = (struct ball_face *)malloc(sizeof(struct ball_face));
-    if (!f)
-	return 0;
+ball_face::ball_face (unsigned int radius, cairo_surface_t * face, int rotation) {
     if (face && rotation) {
-	f->rotations = 2*M_PI * radius / linear_rotation_unit;
+	rotations = 2*M_PI * radius / linear_rotation_unit;
     } else {
-	f->rotations = 1;
+	rotations = 1;
     }
-    f->c_faces = (cairo_surface_t **)malloc(sizeof(cairo_surface_t *)*f->rotations);
-    if (!f->c_faces) {
-	free(f);
-	return 0;
-    }
-    for (unsigned int i = 0; i < f->rotations; ++i) {
-	f->c_faces[i] = gdk_window_create_similar_surface(gtk_widget_get_window(canvas),
-							  CAIRO_CONTENT_COLOR_ALPHA,
-							  2*radius, 2*radius);
-	assert(f->c_faces[i]);
-	cairo_t * ball_cr = cairo_create(f->c_faces[i]);
+    c_faces.resize(rotations);
+    for (unsigned int i = 0; i < rotations; ++i) {
+	c_faces[i] = gdk_window_create_similar_surface(gtk_widget_get_window(canvas),
+						       CAIRO_CONTENT_COLOR_ALPHA,
+						       2*radius, 2*radius);
+	assert(c_faces[i]);
+	cairo_t * ball_cr = cairo_create(c_faces[i]);
 	cairo_translate(ball_cr, radius, radius);
 	cairo_arc(ball_cr, 0.0, 0.0, radius, 0, 2 * M_PI);
 	cairo_clip(ball_cr);
@@ -167,7 +164,7 @@ static struct ball_face * new_ball_face(unsigned int radius, cairo_surface_t * f
 	if (face) {
 	    int face_x_offset = cairo_image_surface_get_width (face) / 2;
 	    int face_y_offset = cairo_image_surface_get_height (face) / 2;
-	    cairo_rotate(ball_cr, i*2*M_PI/f->rotations);
+	    cairo_rotate(ball_cr, i*2*M_PI/rotations);
 	    cairo_scale (ball_cr, 1.0 * radius / face_x_offset, 1.0 * radius / face_y_offset);
 	    cairo_set_source_surface(ball_cr, face, -face_x_offset, -face_y_offset);
 	    cairo_paint(ball_cr);
@@ -185,10 +182,27 @@ static struct ball_face * new_ball_face(unsigned int radius, cairo_surface_t * f
 	    cairo_fill (ball_cr);
 	    cairo_pattern_destroy (pat);
 	}
-	cairo_surface_flush(f->c_faces[i]);
+	cairo_surface_flush(c_faces[i]);
 	cairo_destroy(ball_cr);
     }
-    return f;
+}
+
+ball_face::~ball_face() {
+    for (auto f : c_faces)
+	cairo_surface_destroy(f);
+}
+
+cairo_surface_t * ball_face::get_surface (double angle) const {
+    unsigned int face_id;
+    if (rotations == 1)
+	face_id = 0;
+    else {
+	face_id = rotations*angle/(2*M_PI);
+	assert(face_id < rotations);
+	if (face_id >= rotations)
+	    face_id %= rotations;
+    }
+    return c_faces[face_id];
 }
 
 static void balls_init_faces () {
@@ -203,69 +217,48 @@ static void balls_init_faces () {
 	}
     }
     if (face_surface) {
-	faces_count = radius_max + 1 - radius_min;
-	faces = (struct ball_face **)malloc(sizeof(struct ball_face *)*faces_count);
-	for (unsigned int i = 0; i < faces_count; ++i)
-	    faces[i] = 0;
-	for(struct ball * b = balls; b != balls + n_balls; ++b) {
+	faces.assign(radius_max + 1 - radius_min, nullptr);
+	for(ball * b = balls; b != balls + n_balls; ++b) {
 	    unsigned int r_idx = b->radius - radius_min;
-	    if (!faces[r_idx])
-		faces[r_idx] = new_ball_face(b->radius, face_surface, face_rotation);
+	    if (faces[r_idx] == nullptr)
+		faces[r_idx] = new ball_face (b->radius, face_surface, face_rotation);
 	    b->face = faces[r_idx];
 	}
 	cairo_surface_destroy (face_surface);
     } else {
-	faces_count = n_balls;
-	faces = (struct ball_face **)malloc(sizeof(struct ball_face *)*faces_count);
+	faces.resize(n_balls);
 	for (unsigned int i = 0; i < n_balls; ++i)
-	    balls[i].face = faces[i] = new_ball_face(balls[i].radius, 0, face_rotation);
+	    balls[i].face = faces[i] = new ball_face (balls[i].radius, 0, face_rotation);
     }
 }
 
+void ball::draw (cairo_t * cr) const {
+    cairo_save (cr);
+    cairo_translate (cr, x - radius, y - radius);
+    cairo_set_source_surface(cr, face->get_surface (angle), 0, 0);
+    cairo_paint(cr);
+    cairo_restore(cr);
+}
+
 void balls_draw (cairo_t * cr) {
-    for (const struct ball * b = balls; b != balls + n_balls; ++b) {
-	cairo_save(cr);
-	cairo_translate(cr, b->x - b->radius, b->y - b->radius);
-	unsigned int face_id;
-	if (b->face->rotations == 1)
-	    face_id = 0;
-	else {
-	    face_id = b->face->rotations*b->angle/(2*M_PI);
-	    assert(face_id < b->face->rotations);
-	    if (face_id >= b->face->rotations)
-		face_id %= b->face->rotations;
-	}
-	cairo_set_source_surface(cr, b->face->c_faces[face_id], 0, 0);
-	cairo_paint(cr);
-	cairo_restore(cr);
-    }
+    for (const ball * b = balls; b != balls + n_balls; ++b)
+	b->draw(cr);
 }
 
 static void balls_destroy_faces () {
-    if (!faces)
-	return;
-    for (unsigned int i = 0; i < faces_count; ++i) {
-	if (faces[i]) {
-	    if (faces[i]->c_faces) {
-		for (unsigned int j = 0; j < faces[i]->rotations; ++j)
-		    cairo_surface_destroy(faces[i]->c_faces[j]);
-		free(faces[i]->c_faces);
-	    }
-	    free(faces[i]);
-	}
-    }
-    free (faces);
-    faces = 0;
-    faces_count = 0;
+    for (ball_face * f : faces)
+	if (f)
+	    delete (f);
+    faces.clear();
 }
 
 void balls_destroy () {
     balls_destroy_faces ();
-    free (balls);
+    delete [] (balls);
 }
 
 void balls_init () {
-    balls = (struct ball *)malloc(sizeof(struct ball)*n_balls);
+    balls = new ball[n_balls];
     assert(balls);
     balls_init_state ();
     balls_init_faces ();
diff --git a/balls.h b/balls.h
index 880f3d3..a8015b0 100644
--- a/balls.h
+++ b/balls.h
@@ -3,9 +3,10 @@
 
 #include <gtk/gtk.h>
 
-struct ball_face;
+class ball_face;
 
-struct ball {
+class ball {
+public:
     double x;
     double y;
     unsigned int radius;
@@ -16,10 +17,12 @@ struct ball {
     double angle;
     double v_angle;
 
-    struct ball_face * face;
+    ball_face * face;
+
+    void draw (cairo_t * cr) const;
 };
 
-extern struct ball * balls;
+extern ball * balls;
 extern unsigned int n_balls;
 
 extern unsigned int radius_min;
@@ -36,9 +39,9 @@ extern int face_rotation;
 
 extern void balls_init ();
 extern void balls_destroy ();
-extern void ball_update_state (struct ball * p);
-extern void ball_elastic_collision (struct ball * p, struct ball * q);
-extern void ball_reposition (struct ball * b);
+extern void ball_update_state (ball * p);
+extern void ball_elastic_collision (ball * p, ball * q);
+extern void ball_reposition (ball * b);
 extern void balls_draw (cairo_t * cr);
 
 #endif
diff --git a/c_index.h b/c_index.h
index fb979f9..1d5087d 100644
--- a/c_index.h
+++ b/c_index.h
@@ -4,7 +4,7 @@
 #include "balls.h"
 
 void c_index_build();
-void c_index_check_collisions(void (*collision)(struct ball *, struct ball *));
+void c_index_check_collisions(void (*collision)(ball *, ball *));
 int c_index_init();
 void c_index_destroy();
 
diff --git a/gravity.h b/gravity.h
index 4620a9e..17a7964 100644
--- a/gravity.h
+++ b/gravity.h
@@ -11,12 +11,12 @@ struct gravity_vector {
 extern void gravity_constant_field (double x, double y);
 extern void gravity_newton_field (double r, double g);
 
-extern void gravity_get_vector (struct gravity_vector * v, const struct ball * b);
+extern void gravity_get_vector (gravity_vector * v, const ball * b);
 
 extern void gravity_draw (cairo_t * cr);
 extern void gravity_change (double dx, double dy);
 extern void gravity_show ();
 
-extern void gravity_collisions (struct ball * begin, struct ball * end);
+extern void gravity_collisions (ball * begin, ball * end);
 
 #endif
diff --git a/spaceship.h b/spaceship.h
index 91f6796..556fe98 100644
--- a/spaceship.h
+++ b/spaceship.h
@@ -1,7 +1,7 @@
 #ifndef SPACESHIP_H_INCLUDED
 #define SPACESHIP_H_INCLUDED
 
-extern struct ball spaceship;
+extern ball spaceship;
 
 extern void spaceship_init_state ();
 extern void spaceship_update_state ();