diff --git a/.gitignore b/.gitignore
index 18adb28..3cd6d16 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 *.dSYM
 main
+build
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..ebf8400
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,22 @@
+CC = gcc
+CFLAGS = -Wall -g
+SRCDIR = src
+BUILDDIR = build
+TARGET = main
+
+SOURCES = $(wildcard $(SRCDIR)/*.c)
+OBJECTS = $(patsubst $(SRCDIR)/%.c, $(BUILDDIR)/%.o, $(SOURCES))
+
+all: $(BUILDDIR)/$(TARGET)
+
+$(BUILDDIR)/$(TARGET): $(OBJECTS)
+	$(CC) $(CFLAGS) -o $@ $^
+
+$(BUILDDIR)/%.o: $(SRCDIR)/%.c
+	@mkdir -p $(BUILDDIR)
+	$(CC) $(CFLAGS) -c -o $@ $<
+
+clean:
+	rm -rf $(BUILDDIR)/*
+
+.PHONY: clean
diff --git a/src/board.c b/src/board.c
new file mode 100644
index 0000000..9850daf
--- /dev/null
+++ b/src/board.c
@@ -0,0 +1,6 @@
+#include "board.h"
+
+PieceColors piece_getColor(const Piece piece) { return Black & piece; }
+Piece piece_getColorlessPiece(const Piece piece) {
+  return piece_getColor(piece) ^ piece;
+}
diff --git a/src/board.h b/src/board.h
new file mode 100644
index 0000000..0c22a98
--- /dev/null
+++ b/src/board.h
@@ -0,0 +1,18 @@
+#ifndef __BOARD_HEADER
+#include "common.h"
+typedef int Piece;
+typedef enum { Pawn = 0, Knight, Bishop, Rook, Queen, King } Pieces;
+typedef enum { White = 0, Black = 8 } PieceColors;
+
+typedef struct {
+  Piece piece;
+  uint row;
+  uint column;
+} Square;
+
+typedef Square Board[64];
+
+PieceColors piece_getColor(const Piece piece);
+Piece piece_getColorlessPiece(const Piece piece);
+
+#endif // !__BOARD_HEADER
diff --git a/src/common.c b/src/common.c
new file mode 100644
index 0000000..4e1b0b4
--- /dev/null
+++ b/src/common.c
@@ -0,0 +1,13 @@
+#include "common.h"
+
+char chrToLower(char chr) {
+  if (chr >= 'A' && chr <= 'Z')
+    return chr + 32;
+  return chr;
+}
+
+char chrToUpper(char chr) {
+  if (chr >= 'a' && chr <= 'z')
+    return chr - 32;
+  return chr;
+}
diff --git a/src/common.h b/src/common.h
new file mode 100644
index 0000000..ee70eac
--- /dev/null
+++ b/src/common.h
@@ -0,0 +1,9 @@
+#ifndef __COMMON_HEADER
+#include <stdbool.h>
+#include <stdio.h>
+typedef unsigned int uint;
+
+char chrToLower(char chr);
+char chrToUpper(char chr);
+
+#endif // !__COMMON_HEADER
diff --git a/main.c b/src/fen.c
similarity index 74%
rename from main.c
rename to src/fen.c
index d0e235e..9fc4218 100644
--- a/main.c
+++ b/src/fen.c
@@ -1,37 +1,4 @@
-#include <stdbool.h>
-#include <stdio.h>
-
-typedef unsigned int uint;
-typedef int Piece;
-typedef char FEN[75];
-typedef enum { Pawn = 0, Knight, Bishop, Rook, Queen, King } Pieces;
-typedef enum { White = 0, Black = 8 } PieceColors;
-
-typedef struct {
-  Piece piece;
-  uint row;
-  uint column;
-} Square;
-
-typedef Square Board[64];
-
-char chrToLower(char chr) {
-  if (chr >= 'A' && chr <= 'Z')
-    return chr + 32;
-  return chr;
-}
-
-char chrToUpper(char chr) {
-  if (chr >= 'a' && chr <= 'z')
-    return chr - 32;
-  return chr;
-}
-
-PieceColors piece_getColor(const Piece piece) { return Black & piece; }
-Piece piece_getColorlessPiece(const Piece piece) {
-  return piece_getColor(piece) ^ piece;
-}
-
+#include "fen.h"
 // Starter fen: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR
 void fen_toBoard(const FEN fen, Board board) {
   uint i = 0;
@@ -48,7 +15,7 @@ void fen_toBoard(const FEN fen, Board board) {
     // Upper case or lower case
     bool is_upper_case;
     if ((is_upper_case = fen_char > 'A' && fen_char < 'Z') ||
-        fen_char > 'a' && fen_char < 'z') {
+        (fen_char > 'a' && fen_char < 'z')) {
       char lowered_char = chrToLower(fen_char);
       Pieces p;
       switch (lowered_char) {
@@ -149,12 +116,3 @@ void fen_fromBoard(const Board board, FEN fen) {
     fen[fen_i++] = fen_char;
   }
 }
-
-int main() {
-  Board board;
-  FEN fen = "rnbqkbnr/ppppp1pp/5p2/8/8/8/PPPPPPPP/RNBQKBNR";
-  fen_toBoard(fen, board);
-  fen_fromBoard(board, fen);
-  printf("%s", fen);
-  return 0;
-}
diff --git a/src/fen.h b/src/fen.h
new file mode 100644
index 0000000..aa2c653
--- /dev/null
+++ b/src/fen.h
@@ -0,0 +1,9 @@
+#ifndef __FEN_HEADER
+#include "board.h"
+#include "common.h"
+
+typedef char FEN[75];
+void fen_fromBoard(const Board board, FEN fen);
+void fen_toBoard(const FEN fen, Board board);
+
+#endif // !__FEN_HEADER
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..5137f03
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,10 @@
+#include "fen.h"
+
+int main() {
+  Board board;
+  FEN fen = "rnbqkbnr/ppppp1pp/5p2/8/8/8/PPPPPPPP/RNBQKBNR";
+  fen_toBoard(fen, board);
+  fen_fromBoard(board, fen);
+  printf("%s", fen);
+  return 0;
+}