Bootstrap - Dropdown menu

Motivations
- Can you find dropdown menu in TRU Board Games Playground?
Bootstrap buttons and dropdowns
- For consistent look and feel, and design templates - There are many topics to read here.
  - Read all in Bootstrap Buttons for <a>, <input>, and <button>.
  - Trial 1: Let's try to write a button of info type.
     <div class='???'> <input type='hidden' name='StartPage' value='SignIn'> Username: <input type='text' name='username'><br> Password: <input type='password' name='password'><br> <input type='submit' class='??? ???' value='Submit'> </div>
  - Read all in Bootstrap Dropdowns.
  - Trial 2: Let's try to write a drop-down menu for TRU Board Games Playground.
     <div class="???"> <button type="button" class="btn btn-primary dropdown-???" data-toggle="???">BGP Menu <span class="caret"></span></button> <ul class="???"> <li><a href="#"><i>n</i>-Puzzle Game</a></li> <li><a href="#">Tic Tac Toe</a></li> <li><a href="#">Mine Sweeper</a></li> <li class="???"></li> <li><a href="#">Log in</a></li> <li><a href="#">Sign in</a></li> </ul> </div>
  - Trial 3: Let's try to write a drop-down menu for TRU Board Games Playground. Another version using <a> and an image. Include a new menu item, 'n-Queens' as well.
     <div class="???"> <a title='Menu' class="dropdown-???" ???="dropdown"> <img src='menu_icon.png' width='50px' height='50px'></img> </a> <ul class="???"> <li><a href="#"><i>n</i>-Puzzle Game</a></li> <li><a href="#">Tic Tac Toe</a></li> <li><a href="#">Mine Sweeper</a></li> ??? <li class="???"></li> <li><a href="#">Log in</a></li> <li><a href="#">Sign in</a></li> </ul> </div>
Lab 3.
- The menu in the next program, lab3_bgp.html, is not properly displayed.
- Find the HTML code for the menu, and fix it, so that the menu is properly displayed.
- Also include a new menu item, n-Queens.
- Let's download and complete the program.
  - lab3_bgp.html
  - menu_icon.png
Learning outcomes

7.2 Bootstrap - Dropdown menu