diff --git a/pyproject.toml b/pyproject.toml
index 1190636..1b4a85d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,11 +31,6 @@ force_grid_wrap = 0
 use_parentheses = true
 line_length = 79
 
-[tool.mypy]
-pretty = true
-show_traceback = true
-allow_redefinition = true
-
 [tool.black]
 line-length = 79
 target-version = ['py38']
@@ -59,3 +54,6 @@ exclude = '''
                      # the root of the project
 )
 '''
+
+[tool.ruff.lint]
+ignore = ["E402"]
diff --git a/src/Year_2023/Day01.py b/src/Year_2023/Day01.py
new file mode 100644
index 0000000..0542db1
--- /dev/null
+++ b/src/Year_2023/Day01.py
@@ -0,0 +1,130 @@
+# --- Day 1: Trebuchet?! ---
+
+# 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?
+
+with open("files/P1.txt") as f:
+    calibration = [line for line in f.read().strip().split()]
+
+
+def part_1():
+    total = 0
+    for value in calibration:
+        digits = [c for c in value if c.isdigit()]
+        if digits:
+            total += int(digits[0] + digits[-1])
+    print(f"The sum of all calibration values is {total}")
+
+
+# --- 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?
+
+import re
+
+words_to_numbers = {
+    "one": "1",
+    "two": "2",
+    "three": "3",
+    "four": "4",
+    "five": "5",
+    "six": "6",
+    "seven": "7",
+    "eight": "8",
+    "nine": "9",
+}
+
+
+def is_letter(char):
+    return "a" <= char <= "z"
+
+
+def extraction(value):
+    word = ""
+    digits = []
+    for c in value:
+        if c.isdigit():
+            digits.append(c)
+            word = ""
+        elif is_letter(c):
+            word += c
+            for w in words_to_numbers:
+                if w in word:
+                    m = re.search(w, word)
+                    if m:
+                        val = m.group(0)
+                        digits.append(words_to_numbers[str(val)])
+                        # keep last letter!
+                        word = c
+                        break
+    return digits
+
+
+def part_2():
+    total = 0
+    for value in calibration:
+        digits = extraction(value)
+        total += int(digits[0] + digits[-1])
+    print(f"The sum of all calibration values is {total}")
+
+
+if __name__ == "__main__":
+    part_1()
+    part_2()