2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							 
							
							
								---
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								id: 5d822fd413a79914d39e98d7
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								title: Part 15
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								challengeType: 0
							 
						 
					
						
							
								
									
										
										
										
											2020-06-24 16:22:14 +09:00 
										
									 
								 
							 
							
								
									
										 
									 
								
							 
							
								 
							 
							
							
								isHidden: true
							 
						 
					
						
							
								
									
										
										
										
											2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							 
							
							
								---
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								## Description
 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< section  id = 'description' > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								To use a variable, just put the variable name in parenthesis with `var`  in front of them like this: `var(--variable-name)` . Add your variable as the value of the `background-color`  property of the `bb1a`  class. Whatever value you gave the variable will be applied to whatever property you use it on. In this case, your variable has the value of `#999` . So `#999`  will be used as the value for the `background-color`  property.
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< / section > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								## Instructions
 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< section  id = 'instructions' > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< / section > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								## Tests
 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< section  id = 'tests' > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								```yml
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								tests:
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  -  text: test-text
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    testString: const bb1aStyle = code.match(/\.bb1a\s*{[\s\S]+?[^}]}/g)[0]; assert(/background-color\s*:\s*var\(\s*--building-color1\s*\)\s*(;|\s*})/g.test(bb1aStyle));
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								```
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< / section > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								## Challenge Seed
 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< section  id = 'challengeSeed' > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< div  id = 'html-seed' > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								```html
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								<!DOCTYPE html> 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< html >     
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  < head > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < title > freeCodeCamp Skyline Project< / title > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < style > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      *  {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        border: 1px solid black;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        box-sizing: border-box;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      body {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 100vh;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        margin: 0;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        overflow: hidden;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .background-buildings {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 100%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 100%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        display: flex;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        flex-direction: column;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        align-items: center;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        --building-color1: #999 ;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1a {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1b {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 80%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1c {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 90%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1d {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 100%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < / style > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  < / head > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  < body > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < div  class = "background-buildings" > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      < div  class = "bb1" > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        < div  class = "bb1a" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        < div  class = "bb1b" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        < div  class = "bb1c" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        < div  class = "bb1d" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  < / body > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< / html > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								```
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< / section > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								## Solution
 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< section  id = 'solution' > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								```html
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								<!DOCTYPE html> 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< html >     
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  < head > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < title > freeCodeCamp Skyline Project< / title > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < style > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      *  {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        border: 1px solid black;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        box-sizing: border-box;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      body {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 100vh;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        margin: 0;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        overflow: hidden;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .background-buildings {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 100%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 100%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        display: flex;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        flex-direction: column;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        align-items: center;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        --building-color1: #999 ;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1a {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        background-color: var(--building-color1);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1b {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 80%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1c {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 90%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      .bb1d {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        width: 100%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        height: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < / style > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  < / head > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  < body > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < div  class = "background-buildings" > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      < div  class = "bb1" > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        < div  class = "bb1a" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        < div  class = "bb1b" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        < div  class = "bb1c" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								        < div  class = "bb1d" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								      < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								    < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								  < / body > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< / html > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								```
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							 
							
							
								< / section >