diff --git a/Makefile b/Makefile
index 0674557..58bb9e6 100644
--- a/Makefile
+++ b/Makefile
@@ -4,9 +4,9 @@ include dreamcast/base.mk
 include dreamcast/common.mk
 include dreamcast/headers.mk
 
-MAKEFILE_PATH := $(abspath $(firstword $(MAKEFILE_LIST)))
-CFLAGS += -I$(dir $(MAKEFILE_PATH))
-CFLAGS += -I$(dir $(MAKEFILE_PATH))dreamcast/
-LIB ?= $(dir $(MAKEFILE_PATH))dreamcast
+MAKEFILE_PATH := $(patsubst %/,%,$(dir $(abspath $(firstword $(MAKEFILE_LIST)))))
+CFLAGS += -I$(MAKEFILE_PATH)
+CFLAGS += -I$(MAKEFILE_PATH)/dreamcast/
+LIB ?= $(MAKEFILE_PATH)/dreamcast
 
 include aoc.mk
diff --git a/day4/input.txt b/day4/input.txt
new file mode 100644
index 0000000..d423a55
--- /dev/null
+++ b/day4/input.txt
@@ -0,0 +1,140 @@
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+XMMAMAAAAAXMMMSSMMMMMXMMMMMAMXMMMMAMMMXAAXXMMXXMMSAMMXMSMMMSMXSSMSMSXMMSMMAMMSMSASMSSSSSSXSMMSAMXXAAXXXAMXSASXMMMAAXAMMSMMXAAXXMASXMMXSXAMAS
+SSSXSSSSMMSAAAMMXASAMMSXSAMASMMAAMXSXSXMMMXSSSMXMAMMMXMMXAMAMAMXMAXMAXXAXMAMMAXAAMAXXXMAXMAAXXXMAMSMMAMSMXSASXMXSSMMXMAMAMSSMSAMSMMAAAXMMSAM
+SAAXXXAAAXSXMSSXXMSASAXASXMAXAMSMSXMASASAMXAAAMXAAXXXMAXSMSASXSASASXSMXMXSMMSMSMMMXMMMSAMMSSMXSMAXAAXMXXAXMMMAMAMAXSXMASXMAXMAMXMAMXMXSAMMMM
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+SSSSXAMXMASMMASAMMXXXAMXMXSMSAMXAASAAXSAMAMMMMAXMMMMMMSXSASMMXMASAXSAMXXSAMXXAAMSMXXXAMXSAMAMASASASAMXXXAXAAMASMMAMSMXMAXXAAXXMMSAMAXMXAMMXM
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+SAXSASMASAMMSAXMMSAMMMAXMAMXMXMSXSASXSMMMAMXSAXAMMMMMMMAMSAAXAMXMMAMAXAMSSXMMSMMMMSSSSSXMXMSXMASMSSMMSMMMSXSASXMSSXMAAXMASAAXSAMXMXSXMXAAMAM
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diff --git a/day4/input.txt.h b/day4/input.txt.h
new file mode 100644
index 0000000..cf98b57
--- /dev/null
+++ b/day4/input.txt.h
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern uint32_t _binary_day4_input_txt_start __asm("_binary_day4_input_txt_start");
+extern uint32_t _binary_day4_input_txt_end __asm("_binary_day4_input_txt_end");
+extern uint32_t _binary_day4_input_txt_size __asm("_binary_day4_input_txt_size");
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/day4/sample1.txt b/day4/sample1.txt
new file mode 100644
index 0000000..1f4eda2
--- /dev/null
+++ b/day4/sample1.txt
@@ -0,0 +1,10 @@
+MMMSXXMASM
+MSAMXMSMSA
+AMXSXMAAMM
+MSAMASMSMX
+XMASAMXAMM
+XXAMMXXAMA
+SMSMSASXSS
+SAXAMASAAA
+MAMMMXMMMM
+MXMXAXMASX
diff --git a/day4/sample1.txt.h b/day4/sample1.txt.h
new file mode 100644
index 0000000..103fa45
--- /dev/null
+++ b/day4/sample1.txt.h
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern uint32_t _binary_day4_sample1_txt_start __asm("_binary_day4_sample1_txt_start");
+extern uint32_t _binary_day4_sample1_txt_end __asm("_binary_day4_sample1_txt_end");
+extern uint32_t _binary_day4_sample1_txt_size __asm("_binary_day4_sample1_txt_size");
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/day4/solution.c b/day4/solution.c
new file mode 100644
index 0000000..f79a3eb
--- /dev/null
+++ b/day4/solution.c
@@ -0,0 +1,34 @@
+static int stride(char * input, int length)
+{
+  for (int i = 0; i < length; i++) {
+    if (input[i] == '\n') {
+      return 0;
+    }
+  }
+  return -1;
+}
+
+static int height(char * input, int length)
+{
+  int rows = 0;
+  for (int i = 0; i < length; i++) {
+    if (input[i] == '\n') {
+      rows += 1;
+    }
+  }
+  if (input[i-1] != '\n') {
+    rows += 1;
+  }
+}
+
+int day4_part1(char * input, int length)
+{
+  char word_search[65536];
+
+  return -1;
+}
+
+int day4_part2(char * input, int length)
+{
+  return -1;
+}
diff --git a/input_dreamcast.inc b/input_dreamcast.inc
index b5ba364..6356925 100644
--- a/input_dreamcast.inc
+++ b/input_dreamcast.inc
@@ -5,6 +5,8 @@
 #include "day3/sample1.txt.h"
 #include "day3/sample2.txt.h"
 #include "day3/input.txt.h"
+#include "day4/sample1.txt.h"
+#include "day4/input.txt.h"
 
 static struct start_size sample[][2] = {
   {
@@ -25,6 +27,12 @@ static struct start_size sample[][2] = {
     { (  char *)&_binary_day3_sample2_txt_start,
       (uint32_t)&_binary_day3_sample2_txt_size   },
   },
+  {
+    { (  char *)&_binary_day4_sample1_txt_start,
+      (uint32_t)&_binary_day4_sample1_txt_size   },
+    { (  char *)&_binary_day4_sample1_txt_start,
+      (uint32_t)&_binary_day4_sample1_txt_size   },
+  },
 };
 
 static struct start_size input[] = {
@@ -34,4 +42,6 @@ static struct start_size input[] = {
     (uint32_t)&_binary_day2_input_txt_size   },
   { (  char *)&_binary_day3_input_txt_start,
     (uint32_t)&_binary_day3_input_txt_size   },
+  { (  char *)&_binary_day4_input_txt_start,
+    (uint32_t)&_binary_day4_input_txt_size   },
 };
diff --git a/runner.inc b/runner.inc
index b7c647d..7690430 100644
--- a/runner.inc
+++ b/runner.inc
@@ -4,9 +4,12 @@ int day2_part1(char * input, int length);
 int day2_part2(char * input, int length);
 int day3_part1(char * input, int length);
 int day3_part2(char * input, int length);
+int day4_part1(char * input, int length);
+int day4_part2(char * input, int length);
 
 part_func solution[][2] = {
   {day1_part1, day1_part2},
   {day2_part1, day2_part2},
   {day3_part1, day3_part2},
+  {day4_part1, day4_part2},
 };
diff --git a/runner_dreamcast.cpp b/runner_dreamcast.cpp
index 2c1b2ab..47a99b7 100644
--- a/runner_dreamcast.cpp
+++ b/runner_dreamcast.cpp
@@ -278,6 +278,5 @@ int main()
     transfer_scene(font, glyphs);
   }
 
-  while (1);
   serial::string("return\n");
 }
diff --git a/solutions.mk b/solutions.mk
index 2e0ce19..abd409e 100644
--- a/solutions.mk
+++ b/solutions.mk
@@ -8,4 +8,7 @@ DAY_OBJ = \
 	day3/sample1.txt.o \
 	day3/sample2.txt.o \
 	day3/input.txt.o \
-	day3/solution.o
+	day3/solution.o \
+	day4/sample1.txt.o \
+	day4/input.txt.o \
+	day4/solution.o