Learn CSS Variables by Building a City Skyline - Step 78

Tell us what’s happening:

stuck here, still not understanding this exactly, please can anybody help explain it .

Your code so far

<!-- file: index.html -->

/* file: styles.css */
/* User Editable Region */

.fb1c {
  width: 100%;
  height: 80%;
  background: repeating-linear-gradient(
      90deg,
      var(--building-color4),
      var(--building-color4) 10%,
      transparent 10%,
      transparent 15%)
    repeating-linear-gradient(90deg,var(--building-color4) 0%,
                var(--building-color4) 10%,
                var(--window-color4) 10%,
                var(--window-color4) 90%);
}

/* User Editable Region */

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36 Edg/125.0.0.0

Challenge Information:

Learn CSS Variables by Building a City Skyline - Step 78

you are missing a comma after the first gradient