Use dash rather than underscore for class attribute.

assets/scss/hugo_cookie_consent.scss

@@ -0,0 +1,72 @@
+#cookie-banner {
+  color: #E2E8F0;
+  background-color: #4A5568;
+  position: fixed;
+  top: 2.5rem;
+  left: 50%;
+  transform: translateX(-50%);
+  width: calc(100vw - 2rem);
+  max-width: 480px;
+  border: 1px solid #e2e2e2;
+  border-radius: 12px;
+  padding: 1rem 1.25rem;
+  box-shadow: 0 0 36px #111;
+  display: flex;
+  align-items: center;
+  gap: 1rem;
+  z-index: 9999;
+  transition: opacity 0.5s ease;
+
+  @media (max-width: 420px) {
+    flex-direction: column;
+    align-items: stretch;
+    gap: 0.75rem;
+  }
+}
+
+#cookie-banner.fade-out {
+  opacity: 0;
+  pointer-events: none;
+}
+
+#cookie-banner p {
+  margin: 0;
+  font-size: 14px;
+  flex: 1;
+}
+
+#cookie-banner .cookie-buttons {
+  display: flex;
+  gap: 0.5rem;
+  flex-shrink: 0;
+
+  @media (max-width: 420px) {
+    width: 100%;
+
+    button {
+      flex: 1;
+    }
+  }
+}
+
+#cookie-banner button {
+  margin: 0.1rem 0;
+  padding: .45rem 1rem;
+  border-radius: 8px;
+  border: 1px solid #ccc;
+  cursor: pointer;
+  font-size: 13px;
+  white-space: nowrap;
+}
+
+#cookie-accept {
+  background: #4A5E52; color: #fff; border-color: #1a1a1a;
+}
+
+#cookie-decline {
+  background: #2D3748; color: #fff; border-color: #1a1a1a;
+}
+
+#cookie-settings-button {
+  background: #272b2e; color: #fff; border-color: #1a1a1a;
+}

assets/scss/hugo_cookie_consent/style.scss

@@ -1,39 +0,0 @@
-#cookie-banner {
-  position: fixed;
-  top: 2.5rem;
-  left: 50%;
-  transform: translateX(-50%);
-  width: min(480px, calc(100vw - 2rem));
-  background: #fff;
-  border: 1px solid #e2e2e2;
-  border-radius: 12px;
-  padding: 1rem 1.25rem;
-  box-shadow: 0 4px 24px rgba(0,0,0,.08);
-  display: flex;
-  align-items: center;
-  gap: 1rem;
-  z-index: 9999;
-  transition: opacity 0.5s ease;
-}
-
-#cookie-banner.fade-out {
-  opacity: 0;
-  pointer-events: none;
-}
-
-#cookie-banner p { margin: 0; font-size: 14px; flex: 1; }
-
-#cookie-banner button {
-  margin: 0.1rem 0;
-  padding: .45rem 1rem;
-  border-radius: 8px;
-  border: 1px solid #ccc;
-  cursor: pointer;
-  font-size: 13px;
-  white-space: nowrap;
-}
-
-#cookie-accept {
-  background: #0b913a; color: #fff; border-color: #1a1a1a;
-}
-

layouts/_partials/hugo_cookie_consent/banner.html

@@ -8,7 +8,7 @@
       {{ i18n "cookie_more_info" }}
     </a>
   </p>
-  <div>
+  <div class="cookie-buttons">
     <button id="cookie-accept">
       {{ i18n "cookie_button_accept" }}
     </button>

layouts/_shortcodes/hugo_cookie_consent/settings.html

@@ -1,12 +1,12 @@
 <p>
   {{ i18n "cookie_status" }}:
-  <strong id="cookie_status"
+  <strong id="cookie-status"
     data-accepted="{{ i18n "cookie_accepted" }}"
     data-declined="{{ i18n "cookie_declined" }}"
     data-none="{{ i18n "cookie_none" }}">
     &mdash;
   </strong>
 </p>
-<button onclick="reopenCookieBanner()">
+<button id="cookie-settings-button" onclick="reopenCookieBanner()">
   {{ i18n "cookie_change" }}
 </button>