2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							
							
								---
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								id: 5d822fd413a79914d39e98df
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								title: Part 23
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								challengeType: 0
							 
						 
					
						
							
								
									
										
										
										
											2021-01-13 03:31:00 +01:00 
										
									 
								 
							 
							
								
									
										 
								
							 
							
								 
							
							
								dashedName: part-23
							 
						 
					
						
							
								
									
										
										
										
											2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							
							
								---
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
											2020-11-27 19:02:05 +01:00 
										
									 
								 
							 
							
								
									
										 
								
							 
							
								 
							
							
								# --description--
  
						 
					
						
							
								
									
										
										
										
											2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								Hmm, I'm not sure why that didn't work. You can add a fallback value to a variable by putting it as the second value of where you use the variable like this: `var(--variable-name, fallback-value)` . The property will use the fallback value when there's a problem with the variable. Add a fallback value of `green`  to the `background-color`  of `bb2` .
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
											2020-11-27 19:02:05 +01:00 
										
									 
								 
							 
							
								
									
										 
								
							 
							
								 
							
							
								# --hints--
  
						 
					
						
							
								
									
										
										
										
											2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
											2020-11-27 19:02:05 +01:00 
										
									 
								 
							 
							
								
									
										 
								
							 
							
								 
							
							
								test-text
							 
						 
					
						
							
								
									
										
										
										
											2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
											2020-11-27 19:02:05 +01:00 
										
									 
								 
							 
							
								
									
										 
								
							 
							
								 
							
							
								```js
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								const bb2style = code.match(/\.bb2\s*{[\s\S]+?[^}]}/g)[0];
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								assert(
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  /background-color\s*:\s*var\(\s*--building-color2\s*,\s*green\s*\)\s*(;|\s*})/g.test(
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								    bb2style
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  )
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								);
							 
						 
					
						
							
								
									
										
										
										
											2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							
							
								```
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
											2020-11-27 19:02:05 +01:00 
										
									 
								 
							 
							
								
									
										 
								
							 
							
								 
							
							
								# --seed--
  
						 
					
						
							
								
									
										
										
										
											2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
											2020-11-27 19:02:05 +01:00 
										
									 
								 
							 
							
								
									
										 
								
							 
							
								 
							
							
								## --seed-contents--
  
						 
					
						
							
								
									
										
										
										
											2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								```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%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        display: flex;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        align-items: flex-end;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        justify-content: space-evenly;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        display: flex;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        flex-direction: column;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        align-items: center;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        --building-color1: #aa80ff ;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        --building-color2: #66cc99 ;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1a {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color1);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1b {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 80%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color1);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1c {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 90%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color1);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1d {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 100%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color1);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb2 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 50%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color2);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb3 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 55%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb4 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 11%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 58%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								    < / style > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  < / head > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  < body > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								    < div  class = "background-buildings" > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div  class = "bb1" > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        < div  class = "bb1a" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        < div  class = "bb1b" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        < div  class = "bb1c" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        < div  class = "bb1d" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div  class = "bb2" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div  class = "bb3" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div  class = "bb4" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								    < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  < / body > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								< / html >  
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								```
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
											2020-11-27 19:02:05 +01:00 
										
									 
								 
							 
							
								
									
										 
								
							 
							
								 
							
							
								# --solutions--
  
						 
					
						
							
								
									
										
										
										
											2019-11-04 21:01:05 -06:00 
										
									 
								 
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								```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%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        display: flex;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        align-items: flex-end;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        justify-content: space-evenly;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        display: flex;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        flex-direction: column;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        align-items: center;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        --building-color1: #aa80ff ;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        --building-color2: #66cc99 ;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1a {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color1);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1b {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 80%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color1);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1c {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 90%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color1);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb1d {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 100%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 70%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color1);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb2 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 50%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        background-color: var(--building-color2, green);
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb3 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 10%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 55%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      .bb4 {
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        width: 11%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        height: 58%;
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      }
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								    < / style > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  < / head > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  < body > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								    < div  class = "background-buildings" > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div  class = "bb1" > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        < div  class = "bb1a" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        < div  class = "bb1b" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        < div  class = "bb1c" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								        < div  class = "bb1d" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div  class = "bb2" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div  class = "bb3" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div  class = "bb4" > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								      < div > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								    < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								  < / body > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								< / html >  
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								```