diff --git a/2021/nim/common.nim b/2021/nim/common.nim
index d93439c..3940de3 100644
--- a/2021/nim/common.nim
+++ b/2021/nim/common.nim
@@ -1,5 +1,8 @@
 import std/[streams, sequtils, strutils, sugar, strformat, times, httpclient, os, options]
 
+type
+  Lines* = seq[string]
+
 const YEAR = getEnv("AOC_YEAR", "2021").parseInt()
 proc getCookie(): string = "~/.advent-of-code-auth-cookie".expandTilde().readFile()
 proc getCacheDir(): string = joinPath(expandTilde("~/.cache"), fmt"/aoc{YEAR}")
@@ -22,7 +25,7 @@ proc toInts*(s: seq[string]): seq[int] = s.map(parseInt)
 
 proc loadInputText*(day: int): string = day.inputFilePath().readFile().strip()
 
-proc loadInput*(day: int): seq[string] =
+proc loadInput*(day: int): Lines =
   result = collect:
     for l in day.inputStream().lines(): l
 
@@ -48,11 +51,14 @@ proc doDay*[T](
     var p1 = testInput.part1()
     echo "Day ", day, " Part 1: ", p1, " (Expected: ", expectedPart1, ")"
     doAssert p1 == expectedPart1
+
+  time(&"Day {day} Part 1"): echo day.inputLoader().part1()
+
+  when not defined(release):
     var p2 = testInput.part2()
     echo "Day ", day, " Part 2: ", p2, " (Expected: ", expectedPart2, ")"
     doAssert p2 == expectedPart2
 
-  time(&"Day {day} Part 1"): echo day.inputLoader().part1()
   time(&"Day {day} Part 2"): echo day.inputLoader().part2()
 
 proc doDay*[T](
diff --git a/2021/nim/day13.nim b/2021/nim/day13.nim
new file mode 100644
index 0000000..12b3754
--- /dev/null
+++ b/2021/nim/day13.nim
@@ -0,0 +1,69 @@
+import ./common, std/[sequtils, algorithm, sugar, sets, strformat, strutils, tables]
+
+type
+  Axis = enum X, Y
+  Points = HashSet[(int, int)]
+  Fold = (Axis, int)
+  Folds = seq[Fold]
+
+proc parse(input: Lines): (Points, Folds) =
+  var parsingFolds = false
+  for l in input.mapIt it.strip:
+    if l == "": parsingFolds = true; continue
+    if not parsingFolds:
+      let coords = l.split(',').map parseInt
+      result[0].incl (coords[0], coords[1])
+    else:
+      result[1].add ((if l.contains 'x': X else: Y), l.split('=')[1].parseInt)
+
+proc printPoints(points: Points): void =
+  var w, h = 0
+  for (x, y) in points:
+    w = max(w, x)
+    h = max(h, y)
+  var lines: Lines = @[]
+  for y in 0..h: lines.add(' '.repeat(w+1))
+  for (x, y) in points: lines[y][x] = '#'
+  for l in lines: echo l
+
+proc doFold(points: Points, f: Fold): Points =
+  let (axis, n) = f
+  for (x, y) in points:
+    if (axis == X and x > n): result.incl((n - (x - n), y))
+    elif (axis == Y and y > n):
+      result.incl((x, n - (y - n)))
+    else: result.incl((x, y))
+
+proc p1(input: Lines): int =
+  let (points, folds) = input.parse()
+  points.doFold(folds[0]).len()
+
+proc p2(input: Lines): int =
+  let (points, folds) = input.parse()
+  folds.reduce((points: Points, fold) => points.doFold(fold), points).printPoints()
+  echo "You'll have to read this one on your own, captain."
+
+const input = @[
+  "6,10",
+  "0,14",
+  "9,10",
+  "0,3",
+  "10,4",
+  "4,11",
+  "6,0",
+  "6,12",
+  "4,1",
+  "0,13",
+  "10,12",
+  "3,4",
+  "3,0",
+  "8,4",
+  "1,10",
+  "2,14",
+  "8,10",
+  "9,0",
+  "",
+  "fold along y=7",
+  "fold along x=5",
+]
+doDay 13, n => n.loadInput, p1, p2, (input, 17, 0)