プログラマ専用SNS ミクプラ

//カーソル移動処理
	const int HEAD = 0;
	const int TAIL = 3;

	while(ProcessMessage() == 0 && CheckHitKeyAll() != 0 ){}
	while(ProcessMessage() == 0 && CheckHitKeyAll() == 0 ){}
		 //カーソル描画
	DrawBox( 43 , 60 + cursorPos * 30 , 59 , 60 + cursorPos * 30 + 16 , GetColor( 255 , 255 , 0 ),TRUE ) ;
	if( KeyBuf[KEY_INPUT_UP] ==1 )
		cursorPos = (cursorPos == HEAD) ? TAIL : (cursorPos - 1);
	else if( KeyBuf[KEY_INPUT_DOWN] ==1 )
		cursorPos = (cursorPos == TAIL) ? HEAD : (cursorPos + 1);
		
	if( KeyBuf[KEY_INPUT_Z] != 0 )  // 決定処理
	{
	  switch( cursorPos )
	  {
		case 0: setState( 5 ); break;
		case 1: setState( 6 ); break;
		case 2: setState( 7 ); break;
		case 3: setState( 8 ); break;
				//
		default: break;
	  }
	}

全体的にプログラムがおかしい部分があるので、
一から作り直したほうが上手く行くかもしれませんよ。

一応簡単に作ってみたのですが、カーソルで選択するというのは、こんな感じですかね？
（分岐処理への移動はエンターキーになってます）
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#include "DxLib.h"

int Key[256];
int GetHitKeyStateAll_2(int KeyStateBuf[/url]){
        char GetHitKeyStateAll_Key[256];
        GetHitKeyStateAll( GetHitKeyStateAll_Key );
        for(int i=0;i<256;i++){
                if(GetHitKeyStateAll_Key==1) KeyStateBuf++;
                else                            KeyStateBuf=0;
        }
        return 0;
} 

enum StateID{
	STATE_START,
	STATE_CONTINUE,
	STATE_OPTION,
	STATE_EXIT,
	STATE_SELECT,
	STATE_END
};

StateID state = STATE_SELECT;

enum ColorID{
	COLOR_RED,
	COLOR_BLUE,
	COLOR_YELLOW,
	COLOR_GREEN,
	COLOR_CYAN,
	COLOR_WHITE,
	COLOR_MAX
};

int Color[COLOR_MAX];

typedef struct{
	const int r;
	const int g;
	const int b;
}COLOR;

COLOR CList[COLOR_MAX] = {	{ 255,   0,   0},
			{   0,   0, 255},
			{ 255, 255,   0},
			{   0, 255,   0},
			{ 100, 255, 255},
			{ 255, 255, 255}};

typedef struct{
	int PtX;
	int PtY;
	char* str;
	ColorID c;
	const StateID next;
}CHOICES;

CHOICES choices[/url] = {	{100, 100, "START", COLOR_WHITE, STATE_START},
						{100, 120, "CONTINUE",COLOR_WHITE, STATE_CONTINUE},
						{100, 140, "OPTION",COLOR_WHITE,STATE_OPTION},
						{100, 160, "EXIT",COLOR_WHITE, STATE_EXIT}};

void Start(void)
{
	if(Key[KEY_INPUT_Z] == 1){
		state = STATE_SELECT;
	}
	DrawString( 100, 100 , "Start画面です。" ,  Color[COLOR_CYAN]);
	DrawString( 100, 120 , "※Ｚキーで戻ります。" ,  Color[COLOR_WHITE]);
}
void Continue(void)
{
	if(Key[KEY_INPUT_Z] == 1){
		state = STATE_SELECT;
	}
	DrawString( 100, 100 , "Continue画面です。" ,  Color[COLOR_BLUE]);
	DrawString( 100, 120 , "※Ｚキーで戻ります。" ,  Color[COLOR_WHITE]);
}
void Option(void)
{
	if(Key[KEY_INPUT_Z] == 1){
		state = STATE_SELECT;
	}
	DrawString( 100, 100 , "Option画面です。" ,  Color[COLOR_GREEN]);
	DrawString( 100, 120 , "※Ｚキーで戻ります。" ,  Color[COLOR_WHITE]);
}
void Exit(void)
{
	static int count = 150;

	if((--count) == 0)
		state = STATE_END;
	DrawString( 100, 100 , "Exit画面です。" ,  Color[COLOR_RED]);
	DrawString( 100, 120 , "※プログラムを終了します。" ,  Color[COLOR_WHITE]);
}

void Select(void)
{
	static int NowPt = 0;
	static const int ChoiceNum = sizeof(choices)/sizeof(choices[0]);
	
	if(Key[KEY_INPUT_DOWN] == 1 || (Key[KEY_INPUT_DOWN] > 10 && Key[KEY_INPUT_DOWN] % 10 == 0)){
		choices[NowPt].c = COLOR_WHITE;
		NowPt = (NowPt + 1) % ChoiceNum;
	}else if(Key[KEY_INPUT_UP] == 1 || (Key[KEY_INPUT_UP] > 10 && Key[KEY_INPUT_UP] % 10 == 0)){
		choices[NowPt].c = COLOR_WHITE;
		NowPt = (NowPt + ChoiceNum - 1) % ChoiceNum;
	}

	for(int i = 0; i < ChoiceNum; i++){
		if(i == NowPt)
			choices.c = COLOR_YELLOW;
		DrawString( choices.PtX , choices.PtY , choices.str ,  Color[choices.c]);
	}
	DrawString( choices[NowPt].PtX - 20, choices[NowPt].PtY , "⇒" ,  Color[COLOR_CYAN]);

	if(Key[KEY_INPUT_RETURN] == 1){
		state = choices[NowPt].next;
		choices[NowPt].c = COLOR_WHITE;
		NowPt = 0;
	}
}

void SetColor(void)
{
	for(int i = 0, count = sizeof(CList) / sizeof(CList[0]); i < count; i++)
		Color = GetColor(CList.r, CList[i].g, CList[i].b);
}

int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance,LPSTR lpCmdLine, int nCmdShow ){
	ChangeWindowMode( TRUE );

	if(DxLib_Init() == -1 ) return -1;
	SetDrawScreen( DX_SCREEN_BACK );

	SetColor();
	typedef void(*Func)();
	Func fc[/url] = {Start, Continue, Option, Exit, Select};

	while(ProcessMessage()==0 && ClearDrawScreen()==0 && GetHitKeyStateAll_2(Key)==0 && Key[KEY_INPUT_ESCAPE]==0 && state != STATE_END){

		fc[state]();

		ScreenFlip();
	}
	DxLib_End();
	return 0;
}
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