--- id: 5d822fd413a79914d39e98df title: Step 23 challengeType: 0 dashedName: step-23 --- # --description-- 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`. # --hints-- You should add a fallback value of `green` to the `background-color` property. ```js assert.equal(new __helpers.CSSHelp(document).getStyle('.bb2')?.backgroundColor.trim(), 'var(--building-color2, green)'); ``` # --seed-- ## --seed-contents-- ```html City Skyline
``` ```css * { 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); } --fcc-editable-region-- .bb2 { width: 10%; height: 50%; background-color: var(--building-color2); } --fcc-editable-region-- .bb3 { width: 10%; height: 55%; } .bb4 { width: 11%; height: 58%; } ```