diff --git a/sweet_math.c b/sweet_math.c
index 8fe96fb..9045d0e 100644
--- a/sweet_math.c
+++ b/sweet_math.c
@@ -516,6 +516,36 @@ sweet_vector_add4 (vec4 v1, vec4 v2)
     return v1;
 }
 
+vec2
+sweet_vector_middle2 (vec2 vector1, vec2 vector2)
+{
+    vec2 v;
+    v.x = (vector1.x + vector2.x) * 0.5;
+    v.y = (vector1.y + vector2.y) * 0.5;
+    return v;
+}
+    
+vec3
+sweet_vector_middle3 (vec3 vector1, vec3 vector2)
+{
+    vec3 v;
+    v.x = (vector1.x + vector2.x) * 0.5;
+    v.y = (vector1.y + vector2.y) * 0.5;
+    v.z = (vector1.z + vector2.z) * 0.5;
+    return v;
+}
+    
+vec4
+sweet_vector_middle4 (vec4 vector1, vec4 vector2)
+{
+    vec4 v;
+    v.x = (vector1.x + vector2.x) * 0.5;
+    v.y = (vector1.y + vector2.y) * 0.5;
+    v.z = (vector1.z + vector2.z) * 0.5;
+    v.w = (vector1.w + vector2.w) * 0.5;
+    return v;
+}
+
 vec2
 sweet_vector_sub2 (vec2 v1, vec2 v2)
 {
diff --git a/sweet_math.h b/sweet_math.h
index 2ee18b8..52ce27a 100644
--- a/sweet_math.h
+++ b/sweet_math.h
@@ -191,6 +191,14 @@ vec2 sweet_vector_add2 (vec2 vector1, vec2 vector2);
 vec3 sweet_vector_add3 (vec3 vector1, vec3 vector2);
 vec4 sweet_vector_add4 (vec4 vector1, vec4 vector2);
 
+/** Middle */
+/** @param Vector1 as vector */
+/** @param Vector2 as vector */
+/** @return middle point between vector1 and vector2 */
+vec2 sweet_vector_middle2 (vec2 vector1, vec2 vector2);
+vec3 sweet_vector_middle3 (vec3 vector1, vec3 vector2);
+vec4 sweet_vector_middle4 (vec4 vector1, vec4 vector2);
+
 /** Sub */
 /** @param Vector1 as vector */
 /** @param Vector2 as vector */
diff --git a/sweet_matrix.c b/sweet_matrix.c
index b3519cb..4d893c6 100644
--- a/sweet_matrix.c
+++ b/sweet_matrix.c
@@ -242,7 +242,6 @@ mat4
 sweet_matrix_look_at (vec3 pos, vec3 dir, vec3 up)
 {
     mat4 m;
-    mat4 t;
     vec3 side;
     side = sweet_vector_cross (dir, up);
     side = sweet_vector_normalize3 (side);
@@ -885,15 +884,12 @@ sweet_matrix_product4 (mat4 * p, mat4 * a, mat4 * b)
     float bv0 = b->v[0];
     float bv1 = b->v[1];
     float bv2 = b->v[2];
-    float bv3 = b->v[3];
     float bv4 = b->v[4];
     float bv5 = b->v[5];
     float bv6 = b->v[6];
-    float bv7 = b->v[7];
     float bv8 = b->v[8];
     float bv9 = b->v[9];
     float bv10 = b->v[10];
-    float bv11 = b->v[11];
     float bv12 = b->v[12];
     float bv13 = b->v[13];
     float bv14 = b->v[14];
diff --git a/sweet_matrix_stack.c b/sweet_matrix_stack.c
index b2b1dbb..323f367 100644
--- a/sweet_matrix_stack.c
+++ b/sweet_matrix_stack.c
@@ -72,7 +72,7 @@ sweet_matrix_stack4_push (matrix_stack4 * ms)
     if (ms->position >= SWEET_MATRIX_STACK_SIZE) { return 1; }
 
     ms->matrix[ms->position + 1] = ms->matrix[ms->position];
-    ms->position = ms->position++;
+    ms->position++;
     return 0;
 }