I was Suddenly Dropped into a Dungeon.

Our Main Character was having an ordinary day walking to the store for groceries for his family when he suddenly fell into a portal that appeared under him and when he com to, he finds himself in a cave like places with a video games like window in front of him saying [ Hello Human you have encountered a dungeon complete this dungeon to leave] and then it closed without any more information about the dungeon. He confused and yell to get out at first until his cries attracted monsters. Hope you like this story! :3