// internal functions and definitions that are not exported to main program
// ============================================================================
+#include "bd_bdcff.h"
+#include "bd_cave.h"
+#include "bd_cavedb.h"
+#include "bd_caveset.h"
+#include "bd_caveobject.h"
+#include "bd_caveengine.h"
+#include "bd_gameplay.h"
+#include "bd_c64import.h"
+#include "bd_graphics.h"
+#include "bd_sound.h"
+
+
// ----------------------------------------------------------------------------
// constant definitions
// ----------------------------------------------------------------------------
+/* screen sizes and positions for BD engine */
+
+#define TILESIZE 32
+
+extern int TILESIZE_VAR;
+
+#define TILEX TILESIZE_VAR
+#define TILEY TILESIZE_VAR
+
+extern int SCR_FIELDX, SCR_FIELDY;
+
+/* often used screen positions */
+
+extern int SX, SY;
+
+#define SXSIZE (SCR_FIELDX * TILEX)
+#define SYSIZE (SCR_FIELDY * TILEY)
+
+
// ----------------------------------------------------------------------------
// data structure definitions
// ----------------------------------------------------------------------------