/* (PART A) ENTIRE PAGE */
* {
  font-family: Arial, Helvetica, sans-serif;
  box-sizing: border-box;
}
html {
  padding: 0; margin: 0 auto; width: 800px;
  background: #f2f2f2;
}
.header {
  margin: 20px 0; font-weight: 700; 
}
textarea, input, #loader {
  font-size: 16px;
  padding: 10px; margin: 1px; border: 0;
}
input[type="button"], input[type="submit"], #loader {
  color: #fff; background: #3154d5;
  cursor: pointer;
}

/* (PART B) INVOICE */
#inRow { display: flex; }
#inNum { flex-grow: 1; }
#inBill { width: 20%; min-height: 20px; }
#inAdr { width: 50%; min-height: 20px; }
#inTel { width: 20%; min-height: 20px; }
#inDate { flex-grow: 1; }

/* (PART C) ITEMS */
.irow { display: flex; padding: 3px; }
.irow .qty { width: 60px; }
.irow .item { flex-grow: 1; }
.irow .price { width: 120px; }
#itemsList .irow { margin-bottom: 5px; background: #e1e1e1; }
#itemsAdd { margin-top: 10px; background: #d9d9d9; }

/* (PART D) LOAD BUTTON */
#loader { display: inline-block; }
#loader input { display: none; }

/* (PART E) CONTROLS */
#controls {
  padding: 10px; margin-top: 10px;
  background: #d9d9d9;
}