diff --git a/projects/aoc/src/Main.hx b/projects/aoc/src/Main.hx
index 130d77a6..1bb3e257 100644
--- a/projects/aoc/src/Main.hx
+++ b/projects/aoc/src/Main.hx
@@ -3,9 +3,15 @@ package;
 import kiss.Kiss;
 import kiss.Prelude;
 import kiss.List;
+#if year2018
 import year2018.Solutions2018;
+#end
+#if year2020
 import year2020.Solutions2020;
+#end
+#if year2021
 import year2021.Solutions2021;
+#end
 
 @:build(kiss.Kiss.build())
 class Main {}
diff --git a/projects/aoc/src/year2021/Solutions2021.hx b/projects/aoc/src/year2021/Solutions2021.hx
index 89ff3034..ee91930c 100644
--- a/projects/aoc/src/year2021/Solutions2021.hx
+++ b/projects/aoc/src/year2021/Solutions2021.hx
@@ -13,5 +13,7 @@ import year2021.Day4;
 import year2021.Day5;
 #end
 
+using hx.strings.Strings;
+
 @:build(kiss.Kiss.build())
 class Solutions2021 {}
diff --git a/projects/aoc/src/year2021/Solutions2021.kiss b/projects/aoc/src/year2021/Solutions2021.kiss
index 7724d784..8eafd097 100644
--- a/projects/aoc/src/year2021/Solutions2021.kiss
+++ b/projects/aoc/src/year2021/Solutions2021.kiss
@@ -63,11 +63,13 @@
                 realBasins (for =>lp _ realLowPoints (basinAround lp "src/year2021/inputs/day9.txt"))
                 basinSizes (for b realBasins (count b))]
             (assert (= 480 (apply + (for =>_ height realLowPoints (+ 1 height)))))
-            
             (assert (= 1045660 (apply * (.slice (reversed (sort basinSizes)) 0 3))))))
     (dayTodo 10)
     (dayTodo 11)
-    (dayTodo 12)
+    (day 12
+        (load "day12.kiss")
+        (assert (= 10 .length (allPaths "start" "end" "src/year2021/inputs/day12-example.txt")))
+        (assert (= 3421 .length (allPaths "start" "end" "src/year2021/inputs/day12.txt"))))
     (dayTodo 13)
     (dayTodo 14)
     (dayTodo 15)
diff --git a/projects/aoc/src/year2021/day12.kiss b/projects/aoc/src/year2021/day12.kiss
new file mode 100644
index 00000000..89eb0a6d
--- /dev/null
+++ b/projects/aoc/src/year2021/day12.kiss
@@ -0,0 +1,37 @@
+(function link [from to :Map<String,Array<String>> m]
+    (unless (m.exists from)
+        (dictSet m from []))
+    (.push (dictGet m from) to))
+
+(function pathsMap [file]
+    (let [:Map<String,Array<String>> m (new Map)]
+        (doFor line (Util.readLines file)
+            (let [[from to] (line.split "-")]
+                (link from to m)
+                (link to from m)))
+        m))
+
+(function :Array<kiss.List<String>> allPaths [start end file]
+    (let [pMap (pathsMap file)
+            :Array<kiss.List<String>> paths []
+            :Array<Map<String,Bool>> pathsVisited []]
+        (paths.push [start])
+        (let [pathVisited (new Map)]
+            (dictSet pathVisited start true)
+            (pathsVisited.push pathVisited))
+        (until (apply = (concat [end] (for path paths (last path))))
+            (doFor idx (reversed (collect (range paths.length)))
+                (let [path (nth paths idx)
+                        pathVisited (nth pathsVisited idx)
+                        position (last path)]
+                    (when (= end position) (continue))
+                    (paths.splice idx 1)
+                    (pathsVisited.splice idx 1)
+                    (doFor nextPosition (dictGet pMap position)
+                        (unless (dictGet pathVisited nextPosition)
+                            (paths.insert idx (concat (path.copy) [nextPosition]))
+                            (let [nextPathVisited (pathVisited.copy)]
+                                (when (nextPosition.isLowerCase)
+                                    (dictSet nextPathVisited nextPosition true))
+                                (pathsVisited.insert idx nextPathVisited)))))))
+        paths))
\ No newline at end of file
diff --git a/projects/aoc/src/year2021/inputs/day12-example.txt b/projects/aoc/src/year2021/inputs/day12-example.txt
new file mode 100644
index 00000000..898cd568
--- /dev/null
+++ b/projects/aoc/src/year2021/inputs/day12-example.txt
@@ -0,0 +1,7 @@
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end
\ No newline at end of file
diff --git a/projects/aoc/src/year2021/inputs/day12.txt b/projects/aoc/src/year2021/inputs/day12.txt
new file mode 100644
index 00000000..e4501e5a
--- /dev/null
+++ b/projects/aoc/src/year2021/inputs/day12.txt
@@ -0,0 +1,24 @@
+rf-RL
+rf-wz
+wz-RL
+AV-mh
+end-wz
+end-dm
+wz-gy
+wz-dm
+cg-AV
+rf-AV
+rf-gy
+end-mh
+cg-gy
+cg-RL
+gy-RL
+VI-gy
+AV-gy
+dm-rf
+start-cg
+start-RL
+rf-mh
+AV-start
+qk-mh
+wz-mh