add important headers, const ptrs and egg hatch start

include/bg.h

@@ -0,0 +1,43 @@
+#ifndef GUARD_BG_H
+#define GUARD_BG_H
+
+enum
+{
+    BG_CTRL_ATTR_VISIBLE = 1,
+    BG_CTRL_ATTR_CHARBASEINDEX = 2,
+    BG_CTRL_ATTR_MAPBASEINDEX = 3,
+    BG_CTRL_ATTR_SCREENSIZE = 4,
+    BG_CTRL_ATTR_PALETTEMODE = 5,
+    BG_CTRL_ATTR_PRIORITY = 6,
+    BG_CTRL_ATTR_MOSAIC = 7,
+    BG_CTRL_ATTR_WRAPAROUND = 8,
+};
+
+struct BgTemplate
+{
+    u32 bg:2;
+    u32 charBaseIndex:2;
+    u32 mapBaseIndex:5;
+    u32 screenSize:2;
+    u32 paletteMode:1;
+    u32 priority:2;
+    u32 baseTile:10;
+};
+
+void ResetBgsAndClearDma3BusyFlags(u32 leftoverFireRedLeafGreenVariable);
+void InitBgsFromTemplates(u8 bgMode, const struct BgTemplate *templates, u8 numTemplates);
+void SetBgAttribute(u8 bg, u8 attributeId, u8 value);
+u16 GetBgAttribute(u8 bg, u8 attributeId);
+u32 ChangeBgX(u8 bg, u32 value, u8 op);
+u32 GetBgX(u8 bg);
+u32 ChangeBgY(u8 bg, u32 value, u8 op);
+u32 ChangeBgY_ScreenOff(u8 bg, u32 value, u8 op);
+u32 GetBgY(u8 bg);
+void SetBgAffine(u8 bg, u32 srcCenterX, u32 srcCenterY, s16 dispCenterX, s16 dispCenterY, s16 scaleX, s16 scaleY, u16 rotationAngle);
+void SetBgTilemapBuffer(u8 bg, void *tilemap);
+void UnsetBgTilemapBuffer(u8 bg);
+void CopyToBgTilemapBuffer(u8 bg, const void *src, u16 mode, u16 destOffset);
+void CopyBgTilemapBufferToVram(u8 bg);
+u16 LoadBgTiles(u8 bg, const void* src, u16 size, u16 destOffset);
+
+#endif // GUARD_BG_H