/* ==========================================================================
   DFM Deutsche Feinstrom Manufaktur – Stylesheet
   Reines CSS3, keine externen Ressourcen, mobile-first
   ========================================================================== */

:root {
  --color-text: #555555;
  --color-heading: #333333;
  --color-link: #0066bf;
  --color-link-hover: #004a8c;
  --color-bg: #ffffff;
  --color-bg-alt: #f7f7f5;
  --color-header-bg: #efefef;
  --color-border: #e0e0e0;
  --color-footer-bg: #333333;
  --color-footer-text: #dddddd;
  --font-base: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, sans-serif;
  --max-width: 1200px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-base);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  font-size: 16px;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: var(--color-link);
  text-decoration: none;
}

a:hover,
a:focus {
  color: var(--color-link-hover);
  text-decoration: underline;
}

h1, h2, h3, h4 {
  color: var(--color-heading);
  line-height: 1.3;
  font-weight: 600;
}

h1 {
  font-size: 1.7rem;
}

h2 {
  font-size: 1.4rem;
}

h3 {
  font-size: 1.15rem;
}

p {
  margin: 0 0 1em;
}

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.25rem;
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: #fff;
  padding: 0.5em 1em;
  z-index: 1000;
}

.skip-link:focus {
  left: 0.5rem;
  top: 0.5rem;
}

/* ---------- Header ---------- */

.site-header {
  background: var(--color-header-bg);
  border-bottom: 1px solid var(--color-border);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  padding-top: 0.75rem;
  padding-bottom: 0.75rem;
  gap: 0.75rem;
}

.site-logo img {
  max-width: 260px;
  width: 100%;
}

.nav-toggle {
  display: none;
}

.nav-toggle-label {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 40px;
  cursor: pointer;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  background: #fff;
}

.nav-toggle-label span,
.nav-toggle-label span::before,
.nav-toggle-label span::after {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-heading);
  position: relative;
  transition: 0.2s;
}

.nav-toggle-label span::before {
  content: "";
  position: absolute;
  top: -7px;
}

.nav-toggle-label span::after {
  content: "";
  position: absolute;
  top: 7px;
}

.main-nav {
  width: 100%;
  display: none;
  order: 3;
}

.nav-toggle:checked ~ .main-nav {
  display: block;
}

.main-nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  border-top: 1px solid var(--color-border);
}

.main-nav > ul > li {
  border-bottom: 1px solid var(--color-border);
}

.main-nav a {
  display: block;
  padding: 0.75rem 0.25rem;
  color: var(--color-heading);
  font-weight: 600;
}

.main-nav .sub-menu {
  padding-left: 1rem;
  border-top: 1px solid var(--color-border);
}

.main-nav .sub-menu a {
  font-weight: 400;
  font-size: 0.95rem;
}

@media (min-width: 900px) {
  .nav-toggle-label {
    display: none;
  }

  .main-nav {
    display: block;
    width: auto;
    order: 2;
  }

  .main-nav ul {
    display: flex;
    border-top: none;
    gap: 0.25rem;
  }

  .main-nav > ul > li {
    border-bottom: none;
    position: relative;
  }

  .main-nav > ul > li > a {
    padding: 0.5rem 0.85rem;
    border-radius: 4px;
  }

  .main-nav > ul > li:hover > a,
  .main-nav > ul > li:focus-within > a {
    background: #fff;
  }

  .main-nav .sub-menu {
    display: none;
    position: absolute;
    left: 0;
    top: 100%;
    min-width: 240px;
    background: #fff;
    border: 1px solid var(--color-border);
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.08);
    padding: 0.25rem 0;
    z-index: 20;
  }

  .main-nav > ul > li:hover .sub-menu,
  .main-nav > ul > li:focus-within .sub-menu {
    display: block;
  }

  .main-nav .sub-menu a {
    padding: 0.6rem 1rem;
  }
}

/* ---------- Hero / Page intro ---------- */

.page-intro {
  padding: 2rem 0 1rem;
}

.page-intro h1 {
  margin-top: 0;
}

.lead {
  font-size: 1.1rem;
  color: var(--color-heading);
}

/* ---------- Service grid (Startseite) ---------- */

.service-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
  padding: 1.5rem 0 3rem;
}

@media (min-width: 640px) {
  .service-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 980px) {
  .service-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

.service-card {
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.service-card img {
  width: 100%;
  aspect-ratio: 4 / 2.6;
  object-fit: cover;
}

.service-card-body {
  padding: 1rem 1.1rem 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  flex: 1;
}

.service-card-body h2 {
  font-size: 1.1rem;
  margin: 0;
}

.service-card-body p {
  margin: 0;
  font-size: 0.95rem;
}

.service-card-links {
  margin-top: auto;
  padding-top: 0.5rem;
  font-size: 0.9rem;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

/* ---------- Generic content blocks ---------- */

.content {
  padding: 1rem 0 3rem;
}

.content h2 {
  margin-top: 2rem;
}

.content figure {
  margin: 0 0 1.5rem;
}

.content-image {
  width: 100%;
  max-height: 420px;
  object-fit: cover;
  border-radius: 8px;
  margin: 1.5rem 0;
}

.content figcaption {
  font-size: 0.85rem;
  color: #777;
  margin-top: 0.4rem;
}

/* ---------- 404-Fehlerseite ---------- */

.error-page {
  padding: 2.5rem 0 4rem;
  max-width: 700px;
}

.error-code {
  font-size: 4rem;
  font-weight: 700;
  line-height: 1;
  margin: 0;
  color: var(--color-link);
}

.error-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1.5rem 0 2.5rem;
}

.error-links {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.5rem 1.5rem;
  list-style: none;
  padding: 0;
  margin: 0 0 2rem;
}

@media (min-width: 640px) {
  .error-links {
    grid-template-columns: repeat(2, 1fr);
  }
}

.two-col {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
  align-items: start;
}

@media (min-width: 780px) {
  .two-col {
    grid-template-columns: 320px 1fr;
  }
}

.callout {
  background: var(--color-bg-alt);
  border-left: 4px solid var(--color-link);
  padding: 1rem 1.25rem;
  border-radius: 4px;
  margin: 1.5rem 0;
}

.contact-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1rem 0 2rem;
}

.contact-details {
  font-size: 1.15rem;
  line-height: 1.8;
}

.contact-details a {
  font-weight: 600;
}

.btn {
  display: inline-block;
  padding: 0.65rem 1.25rem;
  background: var(--color-link);
  color: #fff !important;
  border-radius: 4px;
  font-weight: 600;
  text-decoration: none !important;
}

.btn:hover {
  background: var(--color-link-hover);
}

.btn-outline {
  background: transparent;
  color: var(--color-link) !important;
  border: 1px solid var(--color-link);
}

.btn-outline:hover {
  background: var(--color-link);
  color: #fff !important;
}

/* ---------- Device grid (Altgeräte / Batterieservice) ---------- */

.device-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
  padding: 1rem 0 2rem;
}

@media (min-width: 640px) {
  .device-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

@media (min-width: 980px) {
  .device-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

.device-card {
  text-align: center;
}

.device-card img {
  border-radius: 6px;
  border: 1px solid var(--color-border);
}

.device-card p {
  font-size: 0.9rem;
  margin-top: 0.5rem;
}

/* ---------- Battery model table (Batterieservice) ---------- */

.model-list {
  display: grid;
  gap: 1.5rem;
  padding: 1rem 0 2rem;
}

.model-card {
  display: grid;
  grid-template-columns: 140px 1fr;
  gap: 1.25rem;
  align-items: start;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 1.25rem;
  background: var(--color-bg-alt);
}

@media (max-width: 520px) {
  .model-card {
    grid-template-columns: 100px 1fr;
  }
}

.model-card img {
  border-radius: 6px;
  border: 1px solid var(--color-border);
  background: #ffffff;
}

.device-card img {
  background: #ffffff;
}

.model-card h3 {
  margin-top: 0;
}

.model-swap {
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
  flex-wrap: wrap;
  margin: 0.4rem 0;
}

.model-swap .arrow {
  color: var(--color-link);
  font-weight: 700;
}

/* ---------- Step list (Batterietausch-Anleitung) ---------- */

.tausch-entry {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.25rem;
  padding: 1.75rem 0;
  border-top: 1px solid var(--color-border);
}

.tausch-entry:first-of-type {
  border-top: none;
}

@media (min-width: 780px) {
  .tausch-entry {
    grid-template-columns: 220px 1fr;
  }
}

.tausch-steps {
  margin: 0.75rem 0 0;
  padding-left: 1.1rem;
}

.tausch-steps li {
  margin-bottom: 0.4rem;
}

/* ---------- Legal pages ---------- */

.legal h2 {
  margin-top: 2rem;
  font-size: 1.2rem;
}

.legal address {
  font-style: normal;
}

/* ---------- Contact form ---------- */

.contact-form {
  display: grid;
  gap: 1rem;
  max-width: 640px;
}

.contact-form label {
  display: block;
  font-weight: 600;
  margin-bottom: 0.35rem;
}

.contact-form input,
.contact-form textarea {
  width: 100%;
  padding: 0.65rem 0.75rem;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font: inherit;
}

.contact-form textarea {
  min-height: 140px;
  resize: vertical;
}

.required {
  color: #c0392b;
}

/* ---------- Footer ---------- */

.site-footer {
  background: var(--color-footer-bg);
  color: var(--color-footer-text);
  margin-top: 2rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
  padding: 2.5rem 0 1.5rem;
}

@media (min-width: 780px) {
  .footer-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.site-footer h2 {
  color: #fff;
  font-size: 1rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-top: 0;
}

.site-footer a {
  color: var(--color-footer-text);
}

.site-footer a:hover {
  color: #fff;
}

.site-footer address {
  font-style: normal;
}

.site-footer ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.site-footer li {
  margin-bottom: 0.5rem;
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.15);
  padding: 1rem 1.25rem;
  text-align: center;
  font-size: 0.85rem;
}

.footer-bottom .container {
  padding: 0;
}

/* ---------- Utility ---------- */

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}