gistfile1.txt

#include "DxLib.h"

float PlayerX = 0;
float PlayerY = 240;
bool RightKeyON = false;

void SetLeftWall(float x);

int WINAPI WinMain(_In_ HINSTANCE, _In_opt_ HINSTANCE, _In_ LPSTR, _In_ int) {
	// ---ここから設定---
	ChangeWindowMode(TRUE), SetMainWindowText("バグりにくい衝突処理"), SetGraphMode(640, 480, 32),
	SetDoubleStartValidFlag(TRUE); DxLib_Init(), SetDrawScreen(DX_SCREEN_BACK);
	// ---ここまで設定---

	// ゲームループ
	while (ScreenFlip() == 0 && ProcessMessage() == 0 && ClearDrawScreen() == 0) {

		RightKeyON = CheckHitKey(KEY_INPUT_RIGHT);

		if (RightKeyON == true) {
			++PlayerX;
		}

		SetLeftWall(320.0f);

		DrawCircle(PlayerX, PlayerY, 30, GetColor(255, 0, 0), true);
	}

	DxLib_End(); return 0;
}

// 左壁の作成
void SetLeftWall(float x) {

	if (x - 3.0f <= PlayerX && PlayerX) {
		if (x - 0.10f <= PlayerX) {
			PlayerX = x - 0.10f;
		}
	}
}