diff --git a/src/engine.rs b/src/engine.rs
index a3690d4..e07355f 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -118,7 +118,9 @@ fn closest_point(level: &Level, pos: &Position, angle: Radian) -> (Tile, Positio
     let mut tile = Tile::Empty;
 
     while tile == Tile::Empty && level.contains(next_point) {
-        if next_point.distance(x_candidate) < next_point.distance(y_candidate) {
+        println!("x_candidate: {:?}, distance: {}", x_candidate, pos.distance(x_candidate));
+        println!("y_candidate: {:?}, distance: {}", y_candidate, pos.distance(y_candidate));
+        if pos.distance(x_candidate) < pos.distance(y_candidate) {
             next_point = x_candidate;
             x_candidate = Position {
                 x: x_candidate.x + x_step.signum(),
@@ -131,16 +133,28 @@ fn closest_point(level: &Level, pos: &Position, angle: Radian) -> (Tile, Positio
                 y: y_candidate.y + y_step.signum(),
             };
         }
-        // println!("next candidate: {:?}", next_point);
+        println!("next candidate: {:?}", next_point);
 
         tile = if next_point.x.fract() == 0.0 {
             let mut position = next_point;
             position.x += 0.5 * x_step.signum();
-            level.tile_at(position)
+            let tile = level.tile_at(position);
+            if tile == Tile::Wall {
+                position.x -= x_step.signum();
+                let opposite_tile = level.tile_at(position);
+                assert_eq!(opposite_tile, Tile::Empty);
+            }
+            tile
         } else {
             let mut position = next_point;
             position.y += 0.5 * y_step.signum();
-            level.tile_at(position)
+            let tile = level.tile_at(position);
+            if tile == Tile::Wall {
+                position.y -= y_step.signum();
+                let opposite_tile = level.tile_at(position);
+                assert_eq!(opposite_tile, Tile::Empty);
+            }
+            tile
         };
     }