diff --git a/.aocrunner.json b/.aocrunner.json
index 6c147be..c5f7fb5 100644
--- a/.aocrunner.json
+++ b/.aocrunner.json
@@ -167,16 +167,16 @@
     },
     {
       "part1": {
-        "solved": false,
-        "result": null,
+        "solved": true,
+        "result": "5576",
         "attempts": [],
-        "time": null
+        "time": 39.91
       },
       "part2": {
-        "solved": false,
-        "result": null,
+        "solved": true,
+        "result": "152837",
         "attempts": [],
-        "time": null
+        "time": 562.6
       }
     },
     {
diff --git a/README.md b/README.md
index d0ed478..6570e21 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,7 @@
 [![Day](https://badgen.net/badge/09/%E2%98%85%E2%98%85/green)](src/day09)
 [![Day](https://badgen.net/badge/10/%E2%98%85%E2%98%85/green)](src/day10)
 [![Day](https://badgen.net/badge/11/%E2%98%85%E2%98%85/green)](src/day11)
-![Day](https://badgen.net/badge/12/%E2%98%86%E2%98%86/gray)
+[![Day](https://badgen.net/badge/12/%E2%98%85%E2%98%85/green)](src/day12)
 ![Day](https://badgen.net/badge/13/%E2%98%86%E2%98%86/gray)
 ![Day](https://badgen.net/badge/14/%E2%98%86%E2%98%86/gray)
 ![Day](https://badgen.net/badge/15/%E2%98%86%E2%98%86/gray)
@@ -146,9 +146,9 @@ Both parts: 11.29ms
 
 ```
 Day 12
-Time part 1: -
-Time part 2: -
-Both parts: -
+Time part 1: 39.91ms
+Time part 2: 562.6ms
+Both parts: 602.51ms
 ```
 
 ```
@@ -243,8 +243,8 @@ Both parts: -
 ```
 
 ```
-Total stars: 22/50
-Total time: 454.25ms
+Total stars: 24/50
+Total time: 1056.76ms
 ```
 
 <!--/RESULTS-->
diff --git a/src/day12/README.md b/src/day12/README.md
new file mode 100644
index 0000000..f43cc54
--- /dev/null
+++ b/src/day12/README.md
@@ -0,0 +1,9 @@
+# 🎄 Advent of Code 2021 - day 12 🎄
+
+## Info
+
+Task description: [link](https://adventofcode.com/2021/day/12)
+
+## Notes
+
+...
\ No newline at end of file
diff --git a/src/day12/index.js b/src/day12/index.js
new file mode 100644
index 0000000..79d1321
--- /dev/null
+++ b/src/day12/index.js
@@ -0,0 +1,90 @@
+import run from "aocrunner"
+
+const parseInput = (rawInput) => rawInput.split`\n`.map((x) => x.split`-`)
+
+const part1 = (rawInput) => {
+  let input = parseInput(rawInput)
+  input = input.concat(input.map(([from, to]) => [to, from]))
+  function countPaths(history) {
+    const here = history[history.length - 1]
+    if (here === "end") {
+      //      console.log(history.join`,`)
+      return 1
+    }
+    const exits = [
+      ...input.filter(
+        ([from, to]) =>
+          from === here && (/[A-Z]+/.test(to) || !history.includes(to)),
+      ),
+    ]
+    return exits.reduce(
+      (acc, [from, to]) => acc + countPaths([...history, to]),
+      0,
+    )
+  }
+  return countPaths(["start"])
+}
+
+const part2 = (rawInput) => {
+  let input = parseInput(rawInput)
+  input = input.concat(input.map(([from, to]) => [to, from]))
+  function countPaths(history, haveDoubled = false) {
+    const here = history[history.length - 1]
+    if (here === "end") {
+      // console.log(history.join`,`)
+      return 1
+    }
+    const exits = [
+      ...input.filter(
+        ([from, to]) =>
+          from === here &&
+          to !== "start" &&
+          (!haveDoubled || /[A-Z]+/.test(to) || !history.includes(to)),
+      ),
+    ]
+    return exits.reduce(
+      (acc, [from, to]) =>
+        acc +
+        countPaths(
+          [...history, to],
+          haveDoubled || (/[a-z]+/.test(to) && history.includes(to)),
+        ),
+      0,
+    )
+  }
+  return countPaths(["start"])
+}
+
+run({
+  part1: {
+    tests: [
+      {
+        input: `start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end`,
+        expected: 10,
+      },
+    ],
+    solution: part1,
+  },
+  part2: {
+    tests: [
+      {
+        input: `start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end`,
+        expected: 36,
+      },
+    ],
+    solution: part2,
+  },
+  trimTestInputs: true,
+})