Small fix

src/cell.rs

@@ -33,4 +33,12 @@ impl Cell {
     pub fn new(variance: CellVariance) -> Self {
         Self { variance }
     }
+
+    pub fn invert(&self) -> Self {
+        Cell::new(match self.variance {
+            CellVariance::DAY => CellVariance::NIGHT,
+            CellVariance::NIGHT => CellVariance::DAY,
+            CellVariance::VOID => CellVariance::VOID
+        })
+    }
 }

src/direction.rs

@@ -8,4 +8,9 @@ impl Direction {
     pub fn new(x: isize, y: isize) -> Self {
         Self { x, y }
     }
+
+    pub fn invert(&mut self) {
+        self.x *= -1;
+        self.y *= -1;
+    }
 }

src/npc.rs

@@ -6,19 +6,73 @@ pub struct NPC {
     pub obstructed_from: Vec<CellVariance>,
     pub pos_x: usize,
     pub pos_y: usize,
-    pub direction: Direction
+    pub direction: Direction,
 }
 
 impl NPC {
-    pub fn new(pos_x: usize, pos_y: usize, direction: Direction, walk_on: CellVariance, obstructed_from: Vec<CellVariance>) -> Self {
-        Self { walk_on, obstructed_from, pos_x, pos_y, direction }
+    pub fn new(
+        pos_x: usize,
+        pos_y: usize,
+        direction: Direction,
+        walk_on: CellVariance,
+        obstructed_from: Vec<CellVariance>,
+    ) -> Self {
+        Self {
+            walk_on,
+            obstructed_from,
+            pos_x,
+            pos_y,
+            direction,
+        }
     }
 
     pub fn new_day(pos_x: usize, pos_y: usize, direction: Direction) -> Self {
-        Self { walk_on: CellVariance::DAY, obstructed_from: vec![CellVariance::NIGHT], pos_x, pos_y, direction }
+        Self {
+            walk_on: CellVariance::DAY,
+            obstructed_from: vec![CellVariance::NIGHT],
+            pos_x,
+            pos_y,
+            direction,
+        }
     }
 
     pub fn new_night(pos_x: usize, pos_y: usize, direction: Direction) -> Self {
-        Self { walk_on: CellVariance::NIGHT, obstructed_from: vec![CellVariance::DAY], pos_x, pos_y, direction }
+        Self {
+            walk_on: CellVariance::NIGHT,
+            obstructed_from: vec![CellVariance::DAY],
+            pos_x,
+            pos_y,
+            direction,
+        }
     }
-}
+
+    pub fn bounce(&mut self) -> Direction {
+        // Get the current and next positions
+        let (curr_x, curr_y) = (self.pos_x as isize, self.pos_y as isize);
+        let (next_x, next_y) = self.next_position();
+        let mut next_direction = self.direction.clone();
+
+        // Hit top from below || Hit bottom from above
+        if curr_y < next_y || curr_y > next_y {
+            next_direction.y *= -1;
+        }
+
+        // Hit right from left || Hit left from right
+        if next_x > curr_x || curr_x > next_x {
+            next_direction.x *= -1;
+        }
+
+        // Return the new bounce direction
+        self.direction = next_direction;
+
+        println!("Next: {:?}", self.direction);
+        self.direction.clone()
+    }
+
+    pub fn next_position(&self) -> (isize, isize) {
+        (
+            (self.pos_x as isize + self.direction.x),
+            (self.pos_y as isize + self.direction.y),
+        )
+    }
+}

src/stage.rs

@@ -148,7 +148,12 @@ impl Stage {
         }
 
         // Draw background
-        for (i, (mut c, pix)) in self.cells.iter().zip(screen.chunks_exact_mut(4)).enumerate() {
+        for (i, (mut c, pix)) in self
+            .cells
+            .iter()
+            .zip(screen.chunks_exact_mut(4))
+            .enumerate()
+        {
             let npc_cell = self.npc_map.get(i).unwrap();
             if let Some(npc_cell) = npc_cell {
                 c = &npc_cell;
@@ -169,25 +174,43 @@ impl Stage {
     }
 
     pub fn update(&mut self) {
-        // TODO: Flying balls
+        let mut hit_cells: Vec<(usize, usize)> = vec![];
+
         for npc in self.npcs.iter_mut() {
-            let next_pos = ((npc.pos_x as isize + npc.direction.x), (npc.pos_y as isize + npc.direction.y));
-            if next_pos.0 < 0 || next_pos.1 < 0 {
-                // TODO: Bounce
-                continue;
+            // if (npc.next_position().0 < 0 || npc.next_position().0 > self.width as isize) ||
+            //     (npc.next_position().1 < 0 || npc.next_position().1 > self.height as isize) {
+            //     npc.bounce();
+            // }
+
+            // Check for collision with window borders
+            if npc.pos_x <= 0 || npc.pos_x >= self.width {
+                // Bounce off horizontally
+                npc.direction.x = -npc.direction.x;
+                // Move object back inside the window
+                npc.pos_x = npc.pos_x.clamp(0, self.width - 1);
+                
             }
 
-            let index = next_pos.0 as usize + next_pos.1 as usize * self.width;
+            if npc.pos_y <= 0 || npc.pos_y >= self.height {
+                // Bounce off vertically
+                npc.direction.y = -npc.direction.y;
+                // Move object back inside the window
+                npc.pos_y = npc.pos_y.clamp(0, self.height - 1);
+            }
+
+            let index =
+                npc.next_position().0 as usize + npc.next_position().1 as usize * self.width;
             let next_cell = self.cells_dup[index];
 
             // If our next cell would be one that we collide with.
             if npc.obstructed_from.contains(&next_cell.variance) {
-                // TODO: Bounce
+                npc.direction.invert();
+                hit_cells.push((npc.pos_x, npc.pos_y));
                 continue;
             }
 
-            npc.pos_x = next_pos.0 as usize;
-            npc.pos_y = next_pos.1 as usize;
+            npc.pos_x = npc.next_position().0 as usize;
+            npc.pos_y = npc.next_position().1 as usize;
 
             // We can move freely for now.
             self.npc_map[index] = Some(Cell::new(npc.obstructed_from[0]));
@@ -198,7 +221,11 @@ impl Stage {
                 let idx = x + y * self.width;
                 // Write into scratch_cells, since we're still reading from `self.cells`
 
-                self.cells_dup[idx] = self.cells[idx];
+                if hit_cells.contains(&(x, y)) {
+                    self.cells_dup[idx] = self.cells[idx].invert();    
+                } else {
+                    self.cells_dup[idx] = self.cells[idx];
+                }
             }
         }