.tool {
  background-color: white;
  border-bottom: 1px solid gray;
}
.clearfix:after {
  content: "";
  clear: both;
  display: block;
}
/* tagsafe */
#left-box {
  width: 43%;
  float: left;
}
#center-box {
  width: 10%;
  float: left;
  margin: 0 2%;
  text-align: center;
}
#right-box {
  width: 43%;
  float: left;
}
#tool {
  width: 80%;
  height: 20%;
  margin: 0 auto;
  padding-top: 20px;
}
#header-box {
  text-align: center;
  margin-bottom: 20px;
  border-bottom: 1px solid gray;
}
#button-box p {
  margin-bottom: 10px;
}
textarea {
  width: 100%;
  height: 350px;
  padding: 10px;
  resize: none;
  border: 1px solid gray;
}
#result {
  resize: none;
  border: 1px solid gray;
}
#button-box button {
  border: 1px solid black;
  padding: 4px 8px;
}

@media screen and (width < 950px) {
  #tool {
    width: 80%;
  }
  #left-box {
    width: 100%;
  }
  #center-box {
    width: 100%;
    margin: 10px 0;
    text-align: center;
  }
  #right-box {
    width: 100%;
  }
  #button-box p:nth-of-type(3) {
    margin-bottom: 0;
  }
}
@media screen and (width < 600px) {
  #tool {
    width: 80%;
  }
  #left-box {
    width: 100%;
  }
  #center-box {
    width: 100%;
    margin: 10px 0;
    text-align: center;
  }
  #right-box {
    width: 100%;
  }
  #button-box p:nth-of-type(3) {
    margin-bottom: 0;
  }
}