diff --git a/core/src/main/scala/tf/bug/aoc/Main.scala b/core/src/main/scala/tf/bug/aoc/Main.scala
index 827527b..79338fa 100644
--- a/core/src/main/scala/tf/bug/aoc/Main.scala
+++ b/core/src/main/scala/tf/bug/aoc/Main.scala
@@ -20,7 +20,6 @@ object Main extends IOApp:
     part.flatMap { p =>
       io.stdinUtf8[IO](1024)
         .through(text.lines)
-        .takeWhile(_.nonEmpty)
         .through(p)
         .through(io.stdoutLines(StandardCharsets.UTF_8))
         .compile.drain
diff --git a/core/src/main/scala/tf/bug/aoc/y2020/Day4.scala b/core/src/main/scala/tf/bug/aoc/y2020/Day4.scala
new file mode 100644
index 0000000..a97f7a9
--- /dev/null
+++ b/core/src/main/scala/tf/bug/aoc/y2020/Day4.scala
@@ -0,0 +1,72 @@
+package tf.bug.aoc.y2020
+
+import cats.effect._
+import cats.parse.{Parser => P, Parser1, Numbers}
+import cats.syntax.all._
+import fs2._
+import tf.bug.aoc.Day
+
+object Day4 extends Day:
+
+  val whitespace: Parser1[Unit] = P.charIn(" ").void
+
+  val parseEntry: Parser1[(String, String)] = (P.length1(3), P.char(':'), P.until1(whitespace)).mapN {
+    case (key, (), value) =>
+      key -> value
+  }
+
+  val parseMap: P[Map[String, String]] = (P.repSep(parseEntry, min = 0, sep = whitespace) <* P.until(P.end)).map(_.toMap)
+
+  override def part1[F[_]: Async]: Pipe[F, String, String] =
+    val requiredKeys = Set(
+      "byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"
+    )
+    parts { m =>
+      val keySet = m.keySet
+      requiredKeys.forall(keySet.contains)
+    }
+
+  override def part2[F[_]: Async]: Pipe[F, String, String] =
+    val hexChar: P[Unit] = P.charIn(('0' to '9') ++ ('a' to 'f')).void
+    val validateColor: P[Unit] = P.char('#') *> hexChar.replicateA(6).void
+    val eyeColors: Set[String] = Set(
+      "amb",
+      "blu",
+      "brn",
+      "gry",
+      "grn",
+      "hzl",
+      "oth",
+    )
+    val pidChar: P[Unit] = Numbers.digit.void
+    val validatePid: P[Unit] = pidChar.replicateA(9).void
+    parts { m =>
+      lazy val validByr = m.get("byr").flatMap(_.toIntOption).fold(false)(x => 1920 <= x && x <= 2002)
+      lazy val validIyr = m.get("iyr").flatMap(_.toIntOption).fold(false)(x => 2010 <= x && x <= 2020)
+      lazy val validEyr = m.get("eyr").flatMap(_.toIntOption).fold(false)(x => 2020 <= x && x <= 2030)
+      lazy val validHgt = m.get("hgt").fold(false) {
+        case s"${hgtCm}cm" =>
+          hgtCm.toIntOption.fold(false)(x => 150 <= x && x <= 193)
+        case s"${hgtIn}in" =>
+          hgtIn.toIntOption.fold(false)(x => 59 <= x && x <= 76)
+        case _ => false
+      }
+      lazy val validHcl = m.get("hcl").fold(false)(validateColor.parseAll(_).isRight)
+      lazy val validEcl = m.get("ecl").fold(false)(eyeColors.contains)
+      lazy val validPid = m.get("pid").fold(false)(validatePid.parseAll(_).isRight)
+      validByr && validIyr && validEyr && validHgt && validHcl && validEcl && validPid
+    }
+
+  def parts[F[_]: Async](validator: Map[String, String] => Boolean): Pipe[F, String, String] =
+    (lines: Stream[F, String]) => {
+      val passportStrings: Stream[F, String] = lines.groupAdjacentBy(_.nonEmpty).collect {
+        case (true, strings) => strings.mkString_(" ")
+      }
+      val passportMaps: Stream[F, Map[String, String]] = passportStrings.map(parseMap.parseAll).collect {
+        case Right(map) => map
+      }
+      passportMaps
+        .map(validator)
+        .foldMap(if(_) 1 else 0)
+        .map(_.show)
+    }
diff --git a/core/src/main/scala/tf/bug/aoc/y2020/y2020.scala b/core/src/main/scala/tf/bug/aoc/y2020/y2020.scala
index 72315a9..d9d47fe 100644
--- a/core/src/main/scala/tf/bug/aoc/y2020/y2020.scala
+++ b/core/src/main/scala/tf/bug/aoc/y2020/y2020.scala
@@ -7,4 +7,5 @@ object y2020 extends Year:
     1 -> Day1,
     2 -> Day2,
     3 -> Day3,
+    4 -> Day4,
   )