diff --git a/bin/back b/bin/back
index 8907ee6..b2da8bc 100755
Binary files a/bin/back and b/bin/back differ
diff --git a/obj/base.o b/obj/base.o
index ef60ff1..a955de7 100644
Binary files a/obj/base.o and b/obj/base.o differ
diff --git a/obj/display.o b/obj/display.o
index 5fe5fd5..145d470 100644
Binary files a/obj/display.o and b/obj/display.o differ
diff --git a/obj/triangles.o b/obj/triangles.o
index c96df28..e578db8 100644
Binary files a/obj/triangles.o and b/obj/triangles.o differ
diff --git a/src/base.c b/src/base.c
index 1eceaf3..82d9ba9 100644
--- a/src/base.c
+++ b/src/base.c
@@ -297,6 +297,14 @@ double distance_pt_cube_3d(double x0, double y0, double z0, cube cb) {
     return distance_pt_cube_0_3d(x0, y0, z0, *cb) ;
 }
 
+double zdepth_of_pt(double x0, double y0, double z0) {
+    double pz0;
+    project_to_camera(x0, y0, z0, NULL, NULL, &pz0);
+    return pz0; 
+}
+
+// ------------------------------------------------------------------------------------------------ //
+
 void project_to_camera(double x0, double y0, double z0, double* rx, double* ry, double* rz) {
     // align pt to (0, 0, 0)
     double x = x0 - camx ;
@@ -314,6 +322,23 @@ void project_to_camera(double x0, double y0, double z0, double* rx, double* ry,
     if(rz != NULL) {*rz = zry*cos(rot_vt) + yry*sin(rot_vt) ;}
 }
 
+void project_to_cube(double x0, double y0, double z0, double* rx, double* ry, double* rz, cube_0 c) {
+    // align pt to (0, 0, 0)
+    double x = x0 - (c.x + c.w/2.0) ;
+    double y = y0 - (c.y + c.h/2.0) ;
+    double z = z0 - (c.z + c.d/2.0) ;
+
+    // rotate (y)
+    double xry = x*cos(c.hz_angle) + z*sin(c.hz_angle) ;
+    double yry = y ;
+    double zry = z*cos(c.hz_angle) - x*sin(c.hz_angle) ;
+
+    // rotate (x)
+    if(rx != NULL) {*rx = xry ;}
+    if(ry != NULL) {*ry = yry*cos(c.vt_angle) - zry*sin(c.vt_angle);}
+    if(rz != NULL) {*rz = zry*cos(c.vt_angle) + yry*sin(c.vt_angle);}
+}
+
 // ------------------------------------------------------------------------------------------------ //
 
 void remove_entity(entity** arr, int* memlen, int* len, int index) {
diff --git a/src/base.h b/src/base.h
index 56d5023..a00fa31 100644
--- a/src/base.h
+++ b/src/base.h
@@ -43,12 +43,14 @@ double distance_pt_cube_0_3d_weighted(double x0, double y0, double z0, double mx
 double distance_pt_cube_axis_max(double coord, double begin, double end);
 double distance_pt_cube_aligned_3d_max(double x0, double y0, double z0, double cx, double cy, double cz, double cw, double ch, double cd);
 double distance_pt_cube_0_3d_max(double x0, double y0, double z0, cube_0 c);
+double zdepth_of_pt(double x0, double y0, double z0);
 
 void remove_entity(entity** arr, int* memlen, int* len, int index);
 void add_entity(entity** arr, int* memlen, int* len, entity ent);
 
 double distance_pt_cube_3d(double x0, double y0, double z0, cube cb);
 void project_to_camera(double x0, double y0, double z0, double* rx, double* ry, double* rz);
+void project_to_cube(double x0, double y0, double z0, double* rx, double* ry, double* rz, cube_0 c);
 
 void import_digits(SDL_Renderer* renderer);
 void import_letters(SDL_Renderer* renderer);
diff --git a/src/display.c b/src/display.c
index 41b24fa..876d58a 100644
--- a/src/display.c
+++ b/src/display.c
@@ -708,22 +708,23 @@ void drawCurrentRoom(SDL_Renderer* renderer) {
     insertionSort_tp(current_room->tps, current_room->tps_size);
     insertionSort_ent(current_room->ents, current_room->ent_len);
 
-    for(int k1 = 0; k1 < current_room->map_size; k1++) {
+    /*for(int k1 = 0; k1 < current_room->map_size; k1++) {
         current_room->map[k1].red = 188 ;
         current_room->map[k1].green = 0 ;
         current_room->map[k1].blue = 0 ;
     }
 
+    int front ;
     for(int k1 = 0; k1 < current_room->map_size; k1++) {
         for(int k2 = k1+1; k2 < current_room->map_size; k2++) {
-            if(cubeOverlap(current_room->map[k1], current_room->map[k2])) {
-                current_room->map[k1].red = 0 ;
+            if(cubeOverlap(current_room->map[k1], current_room->map[k2], &front)) {
+                current_room->map[k1].red = 188*(front==1) ;
                 current_room->map[k1].green = 188 ;
-                current_room->map[k2].red = 0 ;
+                current_room->map[k2].red = 188*(front==-1) ;
                 current_room->map[k2].green = 188 ;
             }
         }
-    }
+    }*/
 
     if(true || draw_type == 0) {
         for(int k = 0; k < current_room->map_size; k++) {
diff --git a/src/triangles.c b/src/triangles.c
index d8cf741..24e2a7f 100644
--- a/src/triangles.c
+++ b/src/triangles.c
@@ -31,11 +31,21 @@ pt_2d* triangle_2 ;
 pt_2d* cube_t1 ;
 pt_2d* cube_t2 ;
 
+int* dOrder1 ;
+int* dOrder2 ;
+
+double* zdepths1 ;
+double* zdepths2 ;
+
 void trInit() {
     triangle_1 = malloc(sizeof(pt_2d)*3);
     triangle_2 = malloc(sizeof(pt_2d)*3);
     cube_t1 = malloc(sizeof(pt_2d)*6);
     cube_t2 = malloc(sizeof(pt_2d)*6);
+    dOrder1 = malloc(sizeof(int)*6);
+    dOrder2 = malloc(sizeof(int)*6);
+    zdepths1 = malloc(sizeof(double)*4);
+    zdepths2 = malloc(sizeof(double)*4);
 }
 
 double det2D(pt_2d* p1, pt_2d* p2, pt_2d* p3) {
@@ -328,7 +338,104 @@ int fillPolygon(int sf, cube_0 c, int trig, pt_2d* ret) {
     }
 }
 
-bool cubeOverlap(cube_0 c1, cube_0 c2) {
+int visibleSurfaces(double x0, double y0, double z0, cube_0 cb, int* dOrd) {
+    // returns the number of surfaces that should be drawn, as well as filling dOrd for said surfaces :
+    // 0 = +x ; 1 = -x
+    // 2 = +y ; 3 = -y
+    // 4 = +z ; 5 = -z
+
+    // align cube center to (0, 0, 0)
+    double x = x0 - (cb.x + cb.w/2.0) ;
+    double y = y0 - (cb.y + cb.h/2.0) ;
+    double z = z0 - (cb.z + cb.d/2.0) ;
+    // rotate (y)
+    double xry = x*cos(cb.hz_angle) + z*sin(cb.hz_angle) ;
+    double yry = y ;
+    double zry = z*cos(cb.hz_angle) - x*sin(cb.hz_angle) ;
+    // rotate (x)
+    double xrx = xry ;
+    double yrx = yry*cos(cb.vt_angle) + zry*sin(cb.vt_angle) ;
+    double zrx = zry*cos(cb.vt_angle) - yry*sin(cb.vt_angle) ;
+    // cube is centered and aligned
+    int id = 0 ;
+    if(xrx > cb.w/2.0) {
+        dOrd[id] = 0 ;
+        id += 1 ;
+    } else if(xrx < -cb.w/2.0) {
+        dOrd[id] = 1 ;
+        id += 1 ;
+    }
+    if(yrx > cb.h/2.0) {
+        dOrd[id] = 2 ;
+        id += 1 ;
+    } else if(yrx < -cb.h/2.0) {
+        dOrd[id] = 3 ;
+        id += 1 ;
+    }
+    if(zrx > cb.d/2.0) {
+        dOrd[id] = 4 ;
+        id += 1 ;
+    } else if(zrx < -cb.d/2.0) {
+        dOrd[id] = 5 ;
+        id += 1 ;
+    }
+    if(id == 0) { // inside the cube
+        for(int k = 0; k < 6; k++) {
+            dOrd[k] = k ;
+        }
+        return 6;
+    } else {
+        return id ;
+    }
+}
+
+void get_zdepths(cube_0 c, int sf, double* ret) {
+    pt_2d campt = to_fpoint(camx, camy, camz);
+    if(sf == 0 || sf == 1) {        // x
+        ret[0] = zdepth_of_pt(c.x + c.w*(sf==0), c.y,       c.z      );
+        ret[1] = zdepth_of_pt(c.x + c.w*(sf==0), c.y + c.h, c.z      );
+        ret[2] = zdepth_of_pt(c.x + c.w*(sf==0), c.y      , c.z + c.d);
+        ret[3] = zdepth_of_pt(c.x + c.w*(sf==0), c.y + c.h, c.z + c.d);
+    } else if(sf == 2 || sf == 3) { // y
+        ret[0] = zdepth_of_pt(c.x,       c.y + c.h*(sf==2), c.z      );
+        ret[1] = zdepth_of_pt(c.x + c.w, c.y + c.h*(sf==2), c.z      );
+        ret[2] = zdepth_of_pt(c.x      , c.y + c.h*(sf==2), c.z + c.d);
+        ret[3] = zdepth_of_pt(c.x + c.w, c.y + c.h*(sf==2), c.z + c.d);
+    } else {                        // z
+        ret[0] = zdepth_of_pt(c.x,       c.y,       c.z + c.d*(sf==4));
+        ret[1] = zdepth_of_pt(c.x + c.w, c.y,       c.z + c.d*(sf==4));
+        ret[2] = zdepth_of_pt(c.x      , c.y + c.h, c.z + c.d*(sf==4));
+        ret[3] = zdepth_of_pt(c.x + c.w, c.y + c.h, c.z + c.d*(sf==4));
+    }
+}
+
+bool is_all_behind(double* back, double* front) {
+    for(int k = 0; k < 3; k++) {
+        if(back[k] > front[k]) {
+            return false;
+        }
+    }
+    return true;
+}
+
+int which_is_in_front(cube_0 c1, int sfc1, cube_0 c2, int sfc2) {
+    int nVis1 = visibleSurfaces(camx, camy, camz, c1, dOrder1);
+    int nVis2 = visibleSurfaces(camx, camy, camz, c2, dOrder2);
+    for(int k1 = 0; k1 < nVis1; k1++) {
+        for(int k2 = 0; k2 < nVis2; k2++) {
+            get_zdepths(c1, dOrder1[k1], zdepths1);
+            get_zdepths(c2, dOrder2[k2], zdepths2);
+            if(is_all_behind(zdepths1, zdepths2)) {
+                return 1;
+            } else if(is_all_behind(zdepths2, zdepths1)) {
+                return -1;
+            }
+        }
+    }
+    return 0;
+}
+
+bool cubeOverlap(cube_0 c1, cube_0 c2, int* retval) {
     int len1 = 0;
     int len2 = 0;
     for(int i1 = 0; i1 < 6; i1++) {
@@ -337,6 +444,7 @@ bool cubeOverlap(cube_0 c1, cube_0 c2) {
                 len1 = fillPolygon(i1, c1, n%2, cube_t1);
                 len2 = fillPolygon(i2, c2, n/2, cube_t2);
                 if(multipleTrianglesIntersection(cube_t1, len1, cube_t2, len2)) {
+                    if(retval != NULL) {*retval = which_is_in_front(c1, i1, c2, i2);}
                     return true;
                 }
             }
diff --git a/src/triangles.h b/src/triangles.h
index ebb7092..631d81f 100644
--- a/src/triangles.h
+++ b/src/triangles.h
@@ -15,6 +15,6 @@ bool triangleIntersectionDec(pt_2d t1_1, pt_2d t1_2, pt_2d t1_3, pt_2d t2_1, pt_
 int returnTriangle(double x0, double y0, double z0, double x1, double y1, double z1, double x2, double y2, double z2, pt_2d* retarr);
 int fillPolygon(int sf, cube_0 c, int trig, pt_2d* ret);
 
-bool cubeOverlap(cube_0 c1, cube_0 c2);
+bool cubeOverlap(cube_0 c1, cube_0 c2, int* retval);
 
 #endif
\ No newline at end of file