diff --git a/2021/10/part1.mjs b/2021/10/part1.mjs
new file mode 100644
index 0000000..adb6152
--- /dev/null
+++ b/2021/10/part1.mjs
@@ -0,0 +1,46 @@
+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+export const processInput = (file) => fs.readFile(file,'utf8').then(
+    content => content.split("\n").filter(x=>x).map(
+        line => line.split('')
+    )
+);
+
+export const closing = {
+    '{':'}',
+    '<': ">",
+    '(': ')',
+    '[': ']',
+};
+
+function firstIllegalCharacter(line) {
+    const stack = [];
+
+    for ( const c of line ) {
+        if( closing[c] ) {
+            stack.push(closing[c]);
+        } else {
+            if(c !== stack.pop())  return c;
+        }
+    }
+
+    return '';
+
+}
+
+export function solution(lines) {
+    const points = {
+        ')': 3,
+        ']': 57,
+        '}': 1197,
+        '>': 25137,
+    }
+
+    return _.sum(
+        lines.map( firstIllegalCharacter ).map(
+            c => points[c] || 0
+        )
+    )
+}
diff --git a/2021/10/part2.mjs b/2021/10/part2.mjs
new file mode 100644
index 0000000..d0003f6
--- /dev/null
+++ b/2021/10/part2.mjs
@@ -0,0 +1,42 @@
+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+import * as p1 from "./part1.mjs";
+
+function completionString(line) {
+    const stack = [];
+
+    for (const c of line) {
+        if (p1.closing[c]) {
+            stack.unshift(p1.closing[c]);
+        } else if (c !== stack.shift()) {
+            return;
+        }
+    }
+
+    return stack;
+}
+
+export function linesScore(lines) {
+    lines = lines.map(completionString).filter((x) => x);
+
+    const points = {
+        ")": 1,
+        "]": 2,
+        "}": 3,
+        ">": 4,
+    };
+
+    const lineScore = (line) => line.reduce((a, b) => 5 * a + points[b], 0);
+
+    return lines.map(lineScore);
+}
+
+export function solution(lines) {
+    const scores = linesScore(lines);
+
+    scores.sort((a, b) => (a < b ? -1 : 1));
+
+    return scores[(scores.length - 1) / 2];
+}
diff --git a/2021/10/sample b/2021/10/sample
new file mode 100644
index 0000000..b1518d9
--- /dev/null
+++ b/2021/10/sample
@@ -0,0 +1,10 @@
+[({(<(())[]>[[{[]{<()<>>
+[(()[<>])]({[<{<<[]>>(
+{([(<{}[<>[]}>{[]{[(<()>
+(((({<>}<{<{<>}{[]{[]{}
+[[<[([]))<([[{}[[()]]]
+[{[{({}]{}}([{[{{{}}([]
+{<[[]]>}<{[{[{[]{()[[[]
+[<(<(<(<{}))><([]([]()
+<{([([[(<>()){}]>(<<{{
+<{([{{}}[<[[[<>{}]]]>[]]
diff --git a/2021/10/test.mjs b/2021/10/test.mjs
new file mode 100644
index 0000000..cc49669
--- /dev/null
+++ b/2021/10/test.mjs
@@ -0,0 +1,23 @@
+// https://adventofcode.com/2021/day/10
+
+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), 26397);
+    t.equal(p1.solution(await input), 311949);
+});
+
+tap.test("part2", async (t) => {
+    t.match(p2.linesScore(await sample), [
+        288957, 5566, 1480781, 995444, 294
+    ]);
+    t.equal(p2.solution(await sample), 288957);
+    t.equal(p2.solution(await input), 3042730309);
+});
diff --git a/2021/_templates/day/new/part1.mjs.t b/2021/_templates/day/new/part1.mjs.t
new file mode 100644
index 0000000..7260703
--- /dev/null
+++ b/2021/_templates/day/new/part1.mjs.t
@@ -0,0 +1,11 @@
+---
+to: '<%= day %>/part1.mjs'
+---
+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+export const processInput = (input) => input;
+
+export function solution(input) {
+}
diff --git a/2021/_templates/day/new/part1.pm.t b/2021/_templates/day/new/part1.pm.t
deleted file mode 100644
index 296e081..0000000
--- a/2021/_templates/day/new/part1.pm.t
+++ /dev/null
@@ -1,15 +0,0 @@
----
-to: '<%= day %>/part1.pm'
----
-package part1;
-
-use 5.34.0;
-use warnings;
-use experimental 'signatures';
-
-use List::AllUtils qw/ /;
-
-sub solution() {
-}
-
-1;
diff --git a/2021/_templates/day/new/part2.mjs.t b/2021/_templates/day/new/part2.mjs.t
new file mode 100644
index 0000000..42c54cc
--- /dev/null
+++ b/2021/_templates/day/new/part2.mjs.t
@@ -0,0 +1,11 @@
+---
+to: '<%= day %>/part2.mjs'
+---
+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+import * as p1 from './part1.mjs';
+
+export function solution(input) {
+}
diff --git a/2021/_templates/day/new/part2.pm.t b/2021/_templates/day/new/part2.pm.t
deleted file mode 100644
index ee431a4..0000000
--- a/2021/_templates/day/new/part2.pm.t
+++ /dev/null
@@ -1,19 +0,0 @@
----
-to: '<%= day %>/part2.pm'
----
-package part2;
-
-use 5.20.0;
-use warnings;
-use experimental 'signatures';
-
-use List::AllUtils qw/ /;
-
-require './part1.pm';
-
-use experimental qw/ signatures postderef /;
-
-sub solution() {
-}
-
-1;
diff --git a/2021/_templates/day/new/test.mjs.t b/2021/_templates/day/new/test.mjs.t
new file mode 100644
index 0000000..ad7240b
--- /dev/null
+++ b/2021/_templates/day/new/test.mjs.t
@@ -0,0 +1,23 @@
+---
+to: '<%= day %>/test.mjs'
+---
+// https://adventofcode.com/2021/day/<%= day %>
+
+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), 0);
+//    t.equal(p1.solution(await input), 0);
+});
+
+tap.test("part2", async (t) => {
+    // t.equal(p2.solution(await sample), 0);
+    // t.equal(p2.solution(await input), 0);
+});
diff --git a/2021/_templates/day/new/tests.t b/2021/_templates/day/new/tests.t
deleted file mode 100644
index 532d04b..0000000
--- a/2021/_templates/day/new/tests.t
+++ /dev/null
@@ -1,20 +0,0 @@
----
-to: '<%= day %>/test.t'
----
-use 5.34.0;
-
-use Test2::V0;
-use Path::Tiny;
-
-require './part1.pm';
-require './part2.pm';
-
-subtest part1 => sub {
-    my $todo = todo 'TODO';
-    is part1::solution( ) => 'TODO';
-};
-
-subtest part2 => sub {
-    my $todo = todo 'TODO';
-    is part2::solution( ) => 'TODO';
-};