diff --git a/main.cpp b/main.cpp
index 0d22f7e..54ec1a3 100644
--- a/main.cpp
+++ b/main.cpp
@@ -26,14 +26,32 @@ struct Vector2d {
   }
 };
 
+
+struct Pedestrian {
+  Vector2d curr_pos;  // $\vectorarrow{r}_\alpha(t)$
+  Vector2d next_pos;  // $\vectorarrow{r}_\alpha(t+1)$ position, curr_pos is needed because when calculating the force on pedestrian j, we need the old pos, not the updated
+  Vector2d curr_vel, next_vel;  // velocity
+  Vector2d destination;  // $\vectorarrow{r}^0_\alpha$
+  Vector2d next_node; // $\vectorarrow{r}^k_\alpha$
+  double v0;  // speed in m/s e.g. 1.34
+  double vMax; // vMax = v0 * 1.3
+  // direction Vector2d e = (dest - curr.position).norm() --> calculate on the fly or part of struct?
+  void update() { curr_pos = next_pos; }
+};
+
+
+// initialize map
 struct Sidewalk{
   int row, col;
   double length, width;
   Sidewalk(int r, int c, double l, double w) : row(r), col(c), length(l), width(w) {}
-};
-
-struct Cell{
-  // TODO: cell stores information such as next neighbor
+  /* X = obstacle
+  |     X      |
+  |   X        |
+  |            |
+  |         X  |
+  |X           |
+  */
 };
 
 // Numer of pedestrians
@@ -72,24 +90,17 @@ void compute_acceleration_term(Vector2d *F_i, Vector2d curr, Vector2d next) {
 
 }
 
-Vector2d get_next_node(Vector2d curr_pos, Vector2d map[]) {
+Vector2d get_next_node(Pedestrian p, Vector2d map[]) {
   // dummy element
-  return Vector2d(curr_pos.x + 1.0, curr_pos.y + 1.0);
+  return Vector2d(p.curr_pos.x + 1.0, p.curr_pos.y + 1.0);
 }
 
-// return the direction between two nodes along the shortest path
-Vector2d get_direction(Vector2d curr_pos, Vector2d next_pos) {
-  double x, y, x1, x2, y1, y2;
-  
-  x1 = curr_pos.x;
-  x2 = next_pos.x;
-  y1 = curr_pos.y;
-  y2 = next_pos.y;
-
-  x = (x2 - x1) / abs(x2 - x1);
-  y = (y2 - y1) / abs(y2 - y1);
-
-  return Vector2d(x, y);
+// return the direction between curr position and destination
+// $\vectorarrow{e}_\alpha(t)$
+Vector2d get_direction(Pedestrian p) {
+  Vector2d diff = p.next_node - p.curr_pos;
+  double length = diff.norm();
+  return (p.next_node - p.curr_pos) / length;
 }
 
 
@@ -143,8 +154,12 @@ int main() {
   // Desired destination of pedestrian $n_p$
   Vector2d r_0[n_p];
 
+  // for each time frame
   for (int t = 0; t < n_iter; t++) {
+    // for each pedestrian
     for (int i = 0; i < n_p; i++) {
+      // update...
+
       for (int itr = 0; itr < n_p; itr++) {
         F[i][itr].reset();
       }
@@ -156,7 +171,7 @@ int main() {
 
       // TODO: Update $\vec{v}_i^{t+1}$
 
-      // TODO: pdate $\vec{r}_i^{t+1}$
+      // TODO: Update $\vec{r}_i^{t+1}$
     }
   }