diff --git a/projects/aoc/src/year2021/Solutions2021.kiss b/projects/aoc/src/year2021/Solutions2021.kiss
index 36e36fe3..01c514b7 100644
--- a/projects/aoc/src/year2021/Solutions2021.kiss
+++ b/projects/aoc/src/year2021/Solutions2021.kiss
@@ -12,7 +12,8 @@
     (day 3
         (load "day3.kiss")
         (let [inputs (Util.readLines "src/year2021/inputs/day3.txt")]
-            (assert (= 845186 (* (rate inputs false) (rate inputs true))))))
+            (assert (= 845186 (* (rate inputs false) (rate inputs true))))
+            (assert (= 4636702 (* (otherRate inputs false) (otherRate inputs true))))))
     (day 4
         (load "day4.kiss")
         (assert (= 4512 (winningScore "src/year2021/inputs/day4-example.txt")))
diff --git a/projects/aoc/src/year2021/day3.kiss b/projects/aoc/src/year2021/day3.kiss
index be00331a..f922998f 100644
--- a/projects/aoc/src/year2021/day3.kiss
+++ b/projects/aoc/src/year2021/day3.kiss
@@ -9,7 +9,7 @@
 (assert (= 22 (binaryStringToDecimal "10110")))
 (assert (= 9 (binaryStringToDecimal "10110" true)))
 
-(function :String mostCommonBit [:String binary]
+(function :String mostCommonBit [:String binary &opt :String tieBreaker]
     (let [&mut ones 0.0
             &mut total 0.0]
         (doFor digit (binary.split "")
@@ -17,7 +17,9 @@
             (case digit
                 ("1" (+= ones 1))
                 (otherwise)))
-        (Std.string (Math.round (/ ones total)))))
+        (if (and tieBreaker (= ones (/ total 2)))
+                tieBreaker
+            (Std.string (Math.round (/ ones total))))))
 
 (function :Int rate [:Array<String> inputs :Bool epsilon]
     (binaryStringToDecimal
@@ -25,4 +27,14 @@
             (for idx (range .length (first inputs))
                 (mostCommonBit (.join (for input inputs (input.charAt idx)) "")))
             "")
-        epsilon))
\ No newline at end of file
+        epsilon))
+
+// Part 2
+(function :Int otherRate [:Array<String> inputs :Bool co2]
+    (doFor idx (range .length (first inputs))
+        (let [mcb (mostCommonBit (.join (for input inputs (input.charAt idx)) "") "1")
+                o2filter ->input (= (input.charAt idx) mcb)
+                co2Filter ->input !(o2filter input)]
+                (set inputs (filter inputs (if co2 co2Filter o2filter))))
+                (when (= 1 inputs.length) (return (binaryStringToDecimal (first inputs)))))
+    null)
\ No newline at end of file