diff --git a/advent-of-code/2023/day_01/.gitignore b/advent-of-code/2023/day_01/.gitignore
new file mode 100644
index 0000000..e71d1ef
--- /dev/null
+++ b/advent-of-code/2023/day_01/.gitignore
@@ -0,0 +1,43 @@
+.gradle
+gradle
+build/
+gradlew*
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### IntelliJ IDEA ###
+/.idea
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Kotlin ###
+.kotlin
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store
diff --git a/advent-of-code/2023/day_01/README.md b/advent-of-code/2023/day_01/README.md
new file mode 100644
index 0000000..ea41060
--- /dev/null
+++ b/advent-of-code/2023/day_01/README.md
@@ -0,0 +1,63 @@
+# Advent of Code 2023 day 1 solution in Kotlin
+
+## Day 1: Trebuchet?!
+
+[Task page](https://adventofcode.com/2023/day/1)
+
+Something is wrong with global snow production, and you've been selected to take a look.
+The Elves have even given you a map; on it, they've used stars to mark the top fifty locations that are likely
+to be having problems.
+
+You've been doing this long enough to know that to restore snow operations,
+you need to check all fifty stars by December 25th.
+
+Collect stars by solving puzzles. Two puzzles will be made available on each day in the Advent calendar;
+the second puzzle is unlocked when you complete the first. Each puzzle grants one star. Good luck!
+
+You try to ask why they can't just use a weather machine ("not powerful enough") and where they're even sending
+you ("the sky") and why your map looks mostly blank ("you sure ask a lot of questions") and hang on did you just say
+the sky ("of course, where do you think snow comes from") when you realize that the Elves are already loading you
+into a trebuchet ("please hold still, we need to strap you in").
+
+As they're making the final adjustments, they discover that their calibration document (your puzzle input) has been
+amended by a very young Elf who was apparently just excited to show off her art skills. Consequently,
+the Elves are having trouble reading the values on the document.
+
+The newly-improved calibration document consists of lines of text; each line originally contained a specific
+calibration value that the Elves now need to recover. On each line, the calibration value can be found by combining
+the first digit and the last digit (in that order) to form a single two-digit number.
+
+For example:
+
+```
+1abc2
+pqr3stu8vwx
+a1b2c3d4e5f
+treb7uchet
+```
+
+In this example, the calibration values of these four lines are 12, 38, 15, and 77. Adding these together produces 142.
+
+Consider your entire calibration document. What is the sum of all of the calibration values?
+
+
+## Part Two
+
+Your calculation isn't quite right. It looks like some of the digits are actually spelled out with letters:
+one, two, three, four, five, six, seven, eight, and nine also count as valid "digits".
+
+Equipped with this new information, you now need to find the real first and last digit on each line. For example:
+
+```
+two1nine
+eightwothree
+abcone2threexyz
+xtwone3four
+4nineeightseven2
+zoneight234
+7pqrstsixteen
+```
+
+In this example, the calibration values are 29, 83, 13, 24, 42, 14, and 76. Adding these together produces 281.
+
+What is the sum of all of the calibration values?
diff --git a/advent-of-code/2023/day_01/build.gradle.kts b/advent-of-code/2023/day_01/build.gradle.kts
new file mode 100644
index 0000000..6397ac9
--- /dev/null
+++ b/advent-of-code/2023/day_01/build.gradle.kts
@@ -0,0 +1,18 @@
+plugins {
+    kotlin("jvm") version "2.0.21"
+}
+
+group = "space.comfycamp"
+version = "1.0"
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation(kotlin("test"))
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
diff --git a/advent-of-code/2023/day_01/gradle.properties b/advent-of-code/2023/day_01/gradle.properties
new file mode 100644
index 0000000..7fc6f1f
--- /dev/null
+++ b/advent-of-code/2023/day_01/gradle.properties
@@ -0,0 +1 @@
+kotlin.code.style=official
diff --git a/advent-of-code/2023/day_01/settings.gradle.kts b/advent-of-code/2023/day_01/settings.gradle.kts
new file mode 100644
index 0000000..bce7d78
--- /dev/null
+++ b/advent-of-code/2023/day_01/settings.gradle.kts
@@ -0,0 +1,2 @@
+rootProject.name = "day_01"
+
diff --git a/advent-of-code/2023/day_01/src/main/kotlin/Calibrator.kt b/advent-of-code/2023/day_01/src/main/kotlin/Calibrator.kt
new file mode 100644
index 0000000..12dc9b2
--- /dev/null
+++ b/advent-of-code/2023/day_01/src/main/kotlin/Calibrator.kt
@@ -0,0 +1,52 @@
+package space.comfycamp
+
+import kotlin.text.iterator
+
+val words = listOf("one", "two", "three", "four", "five", "six", "seven", "eight", "nine")
+
+fun getCalibrationValues(lines: List<String>, replaceWords: Boolean): Int {
+    val processedLines = lines
+        .takeIf{ replaceWords }
+        ?.map{ s -> replaceWords(s) }
+        ?: lines
+
+    return processedLines
+        .map { s -> extractFirstAndLastDigits(s) }
+        .sumOf { pair -> pair.first * 10 + pair.second }
+}
+
+private fun extractFirstAndLastDigits(s: String): Pair<Int, Int> {
+    var firstDigit = '0'
+    var lastDigit = '0'
+
+    for (char in s) {
+        if (!char.isDigit()) {
+            continue
+        }
+
+        lastDigit = char
+        if (firstDigit == '0') {
+            firstDigit = char
+        }
+    }
+
+    return Pair(firstDigit.digitToInt(), lastDigit.digitToInt())
+}
+
+private fun replaceWords(line: String): String {
+    var s = line
+    var i = 0
+    while (i < s.length) {
+        val subStr = s.slice(i..<s.length)
+        for (w in words.indices) {
+            if (!subStr.startsWith(words[w])) {
+                continue
+            }
+
+            s = s.replaceRange(i, i + 1, (w + 1).toString())
+            break
+        }
+        i += 1
+    }
+    return s
+}
diff --git a/advent-of-code/2023/day_01/src/main/kotlin/Main.kt b/advent-of-code/2023/day_01/src/main/kotlin/Main.kt
new file mode 100644
index 0000000..d693d82
--- /dev/null
+++ b/advent-of-code/2023/day_01/src/main/kotlin/Main.kt
@@ -0,0 +1,12 @@
+package space.comfycamp
+
+fun main() {
+    val res = object {}.javaClass.getResource("/input.txt")!!
+    val lines = res.readText().trim().lines()
+
+    val res1 = getCalibrationValues(lines, false)
+    println("Part 1: $res1")
+
+    val res2 = getCalibrationValues(lines, true)
+    println("Part 2: $res2")
+}
diff --git a/advent-of-code/2023/kotlin/src/main/resources/day-01/input.txt b/advent-of-code/2023/day_01/src/main/resources/input.txt
similarity index 99%
rename from advent-of-code/2023/kotlin/src/main/resources/day-01/input.txt
rename to advent-of-code/2023/day_01/src/main/resources/input.txt
index 1379cfb..c50fa2a 100644
--- a/advent-of-code/2023/kotlin/src/main/resources/day-01/input.txt
+++ b/advent-of-code/2023/day_01/src/main/resources/input.txt
@@ -997,4 +997,4 @@ ttmtqrh3four4oneightrkv
 7fjkfdlmhqxtwoxcpssngss
 gsntbddbnone4cjqjmspzcsxmvvthreefive
 56four4one2
-cqmzqbxzfvonevmmmlxsnjr5zfg
\ No newline at end of file
+cqmzqbxzfvonevmmmlxsnjr5zfg
diff --git a/advent-of-code/2023/day_01/src/test/kotlin/CalibratorTest.kt b/advent-of-code/2023/day_01/src/test/kotlin/CalibratorTest.kt
new file mode 100644
index 0000000..44ea71e
--- /dev/null
+++ b/advent-of-code/2023/day_01/src/test/kotlin/CalibratorTest.kt
@@ -0,0 +1,30 @@
+import space.comfycamp.getCalibrationValues
+import kotlin.test.assertEquals
+import kotlin.test.Test
+
+class CalibratorTest {
+    @Test
+    fun testGetCalibrationValues() {
+        val lines = listOf(
+            "1abc2",
+            "pqr3stu8vwx",
+            "a1b2c3d4e5f",
+            "treb7uchet"
+        )
+        assertEquals(142, getCalibrationValues(lines, false))
+    }
+
+    @Test
+    fun testReplaceAndGetCalibrationValues() {
+        val lines = listOf(
+            "two1nine",
+            "eightwothree",
+            "abcone2threexyz",
+            "xtwone3four",
+            "4nineeightseven2",
+            "zoneight234",
+            "7pqrstsixteen"
+        )
+        assertEquals(281, getCalibrationValues(lines, true))
+    }
+}
diff --git a/advent-of-code/2023/kotlin/src/main/kotlin/Solution01.kt b/advent-of-code/2023/kotlin/src/main/kotlin/Solution01.kt
deleted file mode 100644
index aafa966..0000000
--- a/advent-of-code/2023/kotlin/src/main/kotlin/Solution01.kt
+++ /dev/null
@@ -1,45 +0,0 @@
-class Solution01 {
-    fun getCalibrationValues(lines: List<String>, findWords: Boolean): Int {
-        var sum = 0
-
-        lines.forEach {
-            var firstDigit = ""
-            var lastDigit = ""
-
-            var s = it
-            // Required for the second part
-            if (findWords) {
-                s = replaceStrWithDigits(s)
-            }
-
-            for (char in s) {
-                if (char.isDigit()) {
-                    lastDigit = char.toString()
-                    if (firstDigit == "") {
-                        firstDigit = char.toString()
-                    }
-                }
-            }
-
-            sum += (firstDigit + lastDigit).toInt()
-        }
-
-        return sum
-    }
-
-    private fun replaceStrWithDigits(line: String): String {
-        var s = line
-        val words = arrayOf("one", "two", "three", "four", "five", "six", "seven", "eight", "nine")
-        var i = 0
-        while (i < s.length) {
-            for (w in words.indices) {
-                if (s.slice(i..<s.length).startsWith(words[w])) {
-                    s = s.replaceRange(i, i + 1, (w + 1).toString())
-                    break
-                }
-            }
-            i += 1
-        }
-        return s
-    }
-}
diff --git a/advent-of-code/2023/kotlin/src/main/resources/day-01/test-01.txt b/advent-of-code/2023/kotlin/src/main/resources/day-01/test-01.txt
deleted file mode 100644
index 1ba8437..0000000
--- a/advent-of-code/2023/kotlin/src/main/resources/day-01/test-01.txt
+++ /dev/null
@@ -1,4 +0,0 @@
-1abc2
-pqr3stu8vwx
-a1b2c3d4e5f
-treb7uchet
\ No newline at end of file
diff --git a/advent-of-code/2023/kotlin/src/main/resources/day-01/test-02.txt b/advent-of-code/2023/kotlin/src/main/resources/day-01/test-02.txt
deleted file mode 100644
index 4316a6b..0000000
--- a/advent-of-code/2023/kotlin/src/main/resources/day-01/test-02.txt
+++ /dev/null
@@ -1,7 +0,0 @@
-two1nine
-eightwothree
-abcone2threexyz
-xtwone3four
-4nineeightseven2
-zoneight234
-7pqrstsixteen
\ No newline at end of file
diff --git a/advent-of-code/2023/kotlin/src/test/kotlin/Solution01Test.kt b/advent-of-code/2023/kotlin/src/test/kotlin/Solution01Test.kt
deleted file mode 100644
index 00d9fe3..0000000
--- a/advent-of-code/2023/kotlin/src/test/kotlin/Solution01Test.kt
+++ /dev/null
@@ -1,32 +0,0 @@
-import kotlin.test.Test
-import kotlin.test.assertEquals
-
-class Solution01Test {
-    @Test
-    fun testGetCalibrationValues() {
-        val text = ResourceReader().readFile("day-01/test-01.txt")
-        val res = Solution01().getCalibrationValues(text, false)
-        assertEquals(142, res)
-    }
-
-    @Test
-    fun testReplaceStringsAndGetCalibrationValues() {
-        val text = ResourceReader().readFile("day-01/test-02.txt")
-        val res = Solution01().getCalibrationValues(text, true)
-        assertEquals(281, res)
-    }
-
-    @Test
-    fun solvePart1() {
-        val text = ResourceReader().readFile("day-01/input.txt")
-        val res = Solution01().getCalibrationValues(text, false)
-        println(res)
-    }
-
-    @Test
-    fun solvePart2() {
-        val text = ResourceReader().readFile("day-01/input.txt")
-        val res = Solution01().getCalibrationValues(text, true)
-        println(res)
-    }
-}