diff --git a/src/day20.rs b/src/day20.rs
index c05e0a8..ef68cd0 100644
--- a/src/day20.rs
+++ b/src/day20.rs
@@ -12,14 +12,21 @@ pub fn day20() {
 
     let walkable_tiles: Vec<(usize, usize)> = distance_map
         .enumerate()
-        .filter_map(|(x, y, &d)| if d.is_some() { Some((x, y)) } else { None })
+        // get all tiles that have paths to the endpoint
+        .filter_map(|(x, y, &d)| match d {
+            Some(_) => Some((x, y)),
+            None => None,
+        })
         .collect();
-    let tile_pairs = walkable_tiles
+    let all_cheats = walkable_tiles
         .iter()
+        // for all pairs of walkable tiles
         .cartesian_product(walkable_tiles.iter())
-        .filter(|(&(ax, ay), &(bx, by))| !(ax == bx && ay == by));
-    let all_cheats = tile_pairs
+        // excluding tiles that are the same tile
+        .filter(|(&(ax, ay), &(bx, by))| !(ax == bx && ay == by))
+        // excluding tiles that are too far to cheat between
         .filter(|(&(ax, ay), &(bx, by))| taxicab_distance(ax, ay, bx, by) <= CHEAT_DURATION)
+        // get the time saved by going from a to b
         .map(|(&(ax, ay), &(bx, by))| {
             let taxi_distance = taxicab_distance(ax, ay, bx, by) as i64;
             let a_distance_to_end = distance_map.get(ax, ay).unwrap().unwrap() as i64;