diff --git a/2021/08/part1.mjs b/2021/08/part1.mjs
new file mode 100644
index 0000000..b68a952
--- /dev/null
+++ b/2021/08/part1.mjs
@@ -0,0 +1,34 @@
+import fs from "fs-extra";
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+export const digits = {
+    0: 'abcefg', // 6
+    1: 'cf',     // 2
+    2: 'acdeg',  // 5
+    3: 'acdfg',  // 5
+    4: 'bcdf',   // 4
+    5: 'abdfg',  // 5
+    6: 'abdefg', // 6
+    7: 'acf',    // 3
+    8: 'abcdefg',// 7
+    9: 'abcdfg', // 6
+}
+
+export const processInput = (lines) => {
+    return lines.split("\n").filter(x=>x).map( line => {
+        let [ input, output ] = line.split(' | ').map(
+            x => x.split(' ').map( x => x.split('').sort() )
+        );
+
+        return {input, output};
+    }
+    )
+};
+
+/** @return {number} */
+export function solution(lines) {
+    return lines.map(fp.get('output')).flat().filter(
+        x => [2,4,3,7].includes(x.length )
+    ).length
+}
diff --git a/2021/08/part2.mjs b/2021/08/part2.mjs
new file mode 100644
index 0000000..44b32ab
--- /dev/null
+++ b/2021/08/part2.mjs
@@ -0,0 +1,83 @@
+import fp from "lodash/fp.js";
+import _ from "lodash";
+
+import * as p1 from "./part1.mjs";
+
+function decodedDigits(mapping) {
+    const s = fp.invert(mapping);
+
+    return _.flow([
+        fp.invert,
+        fp.mapKeys((k) =>
+            k
+                .split("")
+                .map((l) => s[l])
+                .join("")
+        ),
+        fp.mapKeys((k) => k.split("").sort().join("")),
+    ])(p1.digits);
+}
+
+function guess(unknowns, guessed = {}, inputs) {
+    const [next] = Object.keys(unknowns);
+
+    if (!next) return guessed;
+
+    for (const p of unknowns[next]) {
+        let newUnknowns = fp.mapValues(
+            (s) => s.filter((x) => x !== p),
+            fp.omit(next, unknowns)
+        );
+
+        if (Object.values(newUnknowns).some((s) => s.size === 0)) continue;
+
+        const r = guess(newUnknowns, { ...guessed, [next]: p }, inputs);
+
+        if (!r) continue;
+
+        const solution = decodedDigits(r);
+
+        if (inputs.every((i) => solution.hasOwnProperty(i.join(""))))
+            return r;
+    }
+}
+
+export function findMapping(input) {
+    const values = "abcdefg".split("");
+
+    let possibility = Object.fromEntries(values.map((v) => [v, values]));
+
+    for (const seq of input) {
+        const p = Object.values(p1.digits)
+            .filter((d) => d.length === seq.length)
+            .join("")
+            .split("");
+
+        for (const l of seq) {
+            possibility[l] = _.intersection(possibility[l], p);
+        }
+    }
+
+    // feel cute, might delete later
+    const one = input.find((i) => i.length === 2);
+    const seven = input.find((i) => i.length === 3);
+    const [a] = seven.filter((x) => !one.includes(x));
+
+    possibility = fp.mapValues(fp.reject("a"), possibility);
+
+    possibility[a] = ["a"];
+
+    return guess(possibility, {}, input);
+}
+
+export function decodedOutput({ input, output }) {
+    const mapping = findMapping([...input, ...output]);
+
+    const digits = decodedDigits(mapping);
+
+    return parseInt(output.map((e) => digits[e.join("")]).join(""));
+}
+
+export function solution(input) {
+    return _.sum(input.map(decodedOutput));
+}
diff --git a/2021/08/sample b/2021/08/sample
new file mode 100644
index 0000000..c9f629b
--- /dev/null
+++ b/2021/08/sample
@@ -0,0 +1,10 @@
+be cfbegad cbdgef fgaecd cgeb fdcge agebfd fecdb fabcd edb | fdgacbe cefdb cefbgd gcbe
+edbfga begcd cbg gc gcadebf fbgde acbgfd abcde gfcbed gfec | fcgedb cgb dgebacf gc
+fgaebd cg bdaec gdafb agbcfd gdcbef bgcad gfac gcb cdgabef | cg cg fdcagb cbg
+fbegcd cbd adcefb dageb afcb bc aefdc ecdab fgdeca fcdbega | efabcd cedba gadfec cb
+aecbfdg fbg gf bafeg dbefa fcge gcbea fcaegb dgceab fcbdga | gecf egdcabf bgf bfgea
+fgeab ca afcebg bdacfeg cfaedg gcfdb baec bfadeg bafgc acf | gebdcfa ecba ca fadegcb
+dbcfg fgd bdegcaf fgec aegbdf ecdfab fbedc dacgb gdcebf gf | cefg dcbef fcge gbcadfe
+bdfegc cbegaf gecbf dfcage bdacg ed bedf ced adcbefg gebcd | ed bcgafe cdgba cbgef
+egadfb cdbfeg cegd fecab cgb gbdefca cg fgcdab egfdb bfceg | gbdfcae bgc cg cgb
+gcafb gcf dcaebfg ecagb gf abcdeg gaef cafbge fdbac fegbdc | fgae cfgab fg bagce
diff --git a/2021/08/sample0 b/2021/08/sample0
new file mode 100644
index 0000000..42b3bfd
--- /dev/null
+++ b/2021/08/sample0
@@ -0,0 +1 @@
+acedgfb cdfbe gcdfa fbcad dab cefabd cdfgeb eafb cagedb ab | cdfeb fcadb cdfeb cdbaf
diff --git a/2021/08/test.mjs b/2021/08/test.mjs
new file mode 100644
index 0000000..9c5fc8b
--- /dev/null
+++ b/2021/08/test.mjs
@@ -0,0 +1,34 @@
+// https://adventofcode.com/2021/day/08
+
+import tap from "tap";
+import fs from "fs-extra";
+
+import * as p1 from "./part1.mjs";
+import * as p2 from "./part2.mjs";
+
+const sample0 = fs.readFile("sample0", "utf8").then(p1.processInput);
+const sample = fs.readFile("sample", "utf8").then(p1.processInput);
+const input = fs.readFile("input", "utf8").then(p1.processInput);
+
+tap.test("part1", async (t) => {
+    t.equal(p1.solution(await sample), 26);
+    t.equal(p1.solution(await input), 375);
+});
+
+tap.test("part2", async (t) => {
+    const [ s0 ] = await sample0;
+    t.match(
+        p2.findMapping([...s0.input,...s0.output]), {
+            d: 'a',
+            e: 'b',
+            a: 'c',
+            f: 'd',
+            g: 'e',
+            b: 'f',
+            c: 'g',
+        }
+    );
+    t.match(p2.decodedOutput(s0),5353);
+    t.equal(p2.solution(await sample), 61229);
+    t.equal(p2.solution(await input), 1019355);
+});
diff --git a/friends/eric b/friends/eric
index a85f406..f9f3e07 160000
--- a/friends/eric
+++ b/friends/eric
@@ -1 +1 @@
-Subproject commit a85f4063d48dd84dc366081533e2c17ee479d3d5
+Subproject commit f9f3e070d56e500e5dae053110de58ddfe332972
diff --git a/friends/waltman/2021 b/friends/waltman/2021
index 3c925eb..441da0a 160000
--- a/friends/waltman/2021
+++ b/friends/waltman/2021
@@ -1 +1 @@
-Subproject commit 3c925ebeb9f531a1f0040dc2a48fcbb7ffbb9281
+Subproject commit 441da0a9c244cef1df7efdc34f1e85ff9a11d14e