diff --git a/src/sudoku.c b/src/sudoku.c
new file mode 100644
index 0000000..af93562
--- /dev/null
+++ b/src/sudoku.c
@@ -0,0 +1,37 @@
+// Copyright (c) 2025 Quinn
+// Licensed under the MIT Licence. See LICENSE for details
+#include "sudoku.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "util/intdef.h"
+
+void sudoku_solve_step(u16 *board) {
+	u16 bmask[SUDOKU_DEPTH_2]; // board mask
+	memcpy(bmask, board, SUDOKU_DEPTH_2 * 2);
+	// TODO: first, we must somehow loop through the columns
+	// TODO: then, we must write to the bmask or do *magic* for the bits designating to 1-9 to be unset if ONLY one of them is set
+}
+
+void sudoku_print(const u16 *board) {
+	for (uint i = 0; i < SUDOKU_DEPTH_2; i++) {
+		char tile;
+		switch (board[i]) {
+		case SUDOKU_1: tile = '1'; break;
+		case SUDOKU_2: tile = '2'; break;
+		case SUDOKU_3: tile = '3'; break;
+		case SUDOKU_4: tile = '4'; break;
+		case SUDOKU_5: tile = '5'; break;
+		case SUDOKU_6: tile = '6'; break;
+		case SUDOKU_7: tile = '7'; break;
+		case SUDOKU_8: tile = '8'; break;
+		case SUDOKU_9: tile = '9'; break;
+		default:       tile = ' '; break;
+		};
+
+		printf("|%c ", tile);
+		if (i % 9 == 8) printf("|\n");
+	}
+}
diff --git a/src/sudoku.h b/src/sudoku.h
new file mode 100644
index 0000000..61ed3d8
--- /dev/null
+++ b/src/sudoku.h
@@ -0,0 +1,27 @@
+// Copyright (c) 2025 Quinn
+// Licensed under the MIT Licence. See LICENSE for details
+#pragma once
+
+#include "util/intdef.h"
+
+#define SUDOKU_DEPTH   9                             // defines the "depth" of the puzzle.
+#define SUDOKU_DEPTH_2 (SUDOKU_DEPTH * SUDOKU_DEPTH) // computes how many squares there are
+
+/* bitmask  */
+enum sudoku_bitmask {
+	SUDOKU_1 = 0x001,
+	SUDOKU_2 = 0x002,
+	SUDOKU_3 = 0x004,
+	SUDOKU_4 = 0x008,
+	SUDOKU_5 = 0x010,
+	SUDOKU_6 = 0x020,
+	SUDOKU_7 = 0x040,
+	SUDOKU_8 = 0x080,
+	SUDOKU_9 = 0x100,
+};
+
+/* TODO: write documentation */
+void sudoku_solve_step(u16 *board);
+
+/* TODO: write documentation */
+void sudoku_print(const u16 *board);