diff --git a/2021/12/part1.mjs b/2021/12/part1.mjs
new file mode 100644
index 0000000..8767932
--- /dev/null
+++ b/2021/12/part1.mjs
@@ -0,0 +1,51 @@
+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+import Graph from 'graphology';
+
+
+
+export const processInput = (filename) => fs.readFile(filename,'utf8').then(
+    content => content.split("\n").filter(x=>x)
+).then(
+    lines => {
+        const graph = new Graph();
+        lines.map( line => line.split('-') ).forEach( edge =>
+            graph.mergeEdge(...edge) );
+        return graph;
+    }
+
+);
+
+export function solution(graph) {
+    let paths = 0;
+    const left = [
+        { graph, where: 'start' }
+    ];
+
+    while( left.length > 0 ) {
+        const position = left.shift();
+
+        if( position.where === 'end' ) {
+            paths++;
+            continue;
+        }
+
+        let newGraph = position.graph;
+        if( position.where === position.where.toLowerCase()  ) {
+            newGraph = position.graph.copy();
+            newGraph.dropNode(position.where);
+        }
+
+        for( const n of position.graph.neighbors(position.where) ) {
+            left.unshift({
+                graph: newGraph,
+                where: n,
+            });
+        }
+
+    }
+
+    return paths;
+}
diff --git a/2021/12/part2.mjs b/2021/12/part2.mjs
new file mode 100644
index 0000000..8dfa908
--- /dev/null
+++ b/2021/12/part2.mjs
@@ -0,0 +1,60 @@
+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+import * as p1 from "./part1.mjs";
+
+export function solution(graph) {
+    let paths = 0;
+
+    graph.forEachNode((node) => {
+        graph.setNodeAttribute(node, "nbrVisits", 0);
+    });
+
+    const left = [{ graph, where: "start" }];
+
+    while (left.length > 0) {
+        const position = left.shift();
+
+        if (position.where === "end") {
+            paths++;
+            continue;
+        }
+
+        const canVisit = (graph, node) => {
+            if (node === "start") return false;
+            if (node === node.toUpperCase()) return true;
+            const nbrVisits = graph.getNodeAttribute(node, "nbrVisits");
+
+            if (nbrVisits === 0) return true;
+            if (nbrVisits > 1) return false;
+            return !graph.hasAttribute("revisited");
+        };
+
+        for (const n of position.graph
+            .neighbors(position.where)
+            .filter((n) => canVisit(position.graph, n))) {
+            let newGraph = position.graph;
+
+            if (n === n.toLowerCase()) {
+                newGraph = newGraph.copy();
+                newGraph.updateNodeAttribute(
+                    n,
+                    "nbrVisits",
+                    fp.add(1)
+                );
+
+                if (newGraph.getNodeAttribute(n, "nbrVisits") === 2) {
+                    newGraph.setAttribute("revisited", n);
+                }
+            }
+
+            left.unshift({
+                graph: newGraph,
+                where: n,
+            });
+        }
+    }
+
+    return paths;
+}
diff --git a/2021/12/sample b/2021/12/sample
new file mode 100644
index 0000000..6fd8c41
--- /dev/null
+++ b/2021/12/sample
@@ -0,0 +1,7 @@
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end
diff --git a/2021/12/test.mjs b/2021/12/test.mjs
new file mode 100644
index 0000000..196547b
--- /dev/null
+++ b/2021/12/test.mjs
@@ -0,0 +1,20 @@
+// https://adventofcode.com/2021/day/12
+
+import tap from "tap";
+import fs from "fs-extra";
+
+import * as p1 from "./part1.mjs";
+import * as p2 from "./part2.mjs";
+
+const sample = p1.processInput('sample');
+const input = p1.processInput('input');
+
+tap.test("part1", async (t) => {
+    t.equal(p1.solution(await sample), 10);
+    t.equal(p1.solution(await input), 3450);
+});
+
+tap.test("part2", async (t) => {
+    t.equal(p2.solution(await sample), 36);
+    t.equal(p2.solution(await input), 96528);
+});