/* ============================================================
   primzahltest.de – Hauptstylesheet
   ============================================================ */

/* ---------- CSS-Variablen ---------------------------------- */
:root {
  --clr-primary:       #1a3a5c;
  --clr-primary-light: #2d6a9f;
  --clr-primary-xlight:#e8f0f9;
  --clr-accent:        #0ea5e9;
  --clr-accent-light:  #bae6fd;
  --clr-success:       #16a34a;
  --clr-success-light: #dcfce7;
  --clr-warning:       #ea580c;
  --clr-warning-light: #ffedd5;
  --clr-error:         #dc2626;
  --clr-error-light:   #fee2e2;
  --clr-neutral-50:    #f8fafc;
  --clr-neutral-100:   #f1f5f9;
  --clr-neutral-200:   #e2e8f0;
  --clr-neutral-300:   #cbd5e1;
  --clr-neutral-400:   #94a3b8;
  --clr-neutral-500:   #64748b;
  --clr-neutral-700:   #334155;
  --clr-neutral-900:   #0f172a;
  --clr-text:          #1e293b;
  --clr-text-muted:    #64748b;
  --clr-bg:            #ffffff;
  --clr-bg-alt:        #f8fafc;
  --clr-border:        #e2e8f0;

  --font-sans: system-ui, -apple-system, "Segoe UI", Helvetica, Arial, sans-serif;
  --font-mono: "Cascadia Code", "Fira Code", "Courier New", monospace;

  --sp-1:  4px;
  --sp-2:  8px;
  --sp-3:  12px;
  --sp-4:  16px;
  --sp-5:  20px;
  --sp-6:  24px;
  --sp-8:  32px;
  --sp-10: 40px;
  --sp-12: 48px;
  --sp-16: 64px;
  --sp-20: 80px;
  --sp-24: 96px;

  --radius-sm: 4px;
  --radius:    8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / .05);
  --shadow:    0 1px 3px 0 rgb(0 0 0 / .10), 0 1px 2px -1px rgb(0 0 0 / .10);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / .10), 0 2px 4px -2px rgb(0 0 0 / .10);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / .10), 0 4px 6px -4px rgb(0 0 0 / .10);

  --transition: 150ms ease;
  --nav-height: 64px;
}

/* ---------- Reset ------------------------------------------ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--clr-text);
  background: var(--clr-bg);
  -webkit-font-smoothing: antialiased;
}
img, video { max-width: 100%; height: auto; display: block; }
a { color: var(--clr-primary-light); text-decoration: none; }
a:hover { text-decoration: underline; }
a:focus-visible { outline: 2px solid var(--clr-accent); outline-offset: 2px; border-radius: var(--radius-sm); }
ul, ol { list-style: none; }
button { cursor: pointer; font-family: inherit; }
input, select, textarea { font-family: inherit; }
table { border-collapse: collapse; width: 100%; }

/* ---------- Container -------------------------------------- */
.container { max-width: 1200px; margin-inline: auto; padding-inline: var(--sp-6); }
@media (min-width: 640px)  { .container { padding-inline: var(--sp-8); } }
@media (min-width: 1280px) { .container { padding-inline: var(--sp-4); } }

/* ---------- Navigation ------------------------------------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--clr-primary);
  box-shadow: var(--shadow-md);
  height: var(--nav-height);
}
.nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  gap: var(--sp-6);
}
.nav__logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: #ffffff;
  letter-spacing: -.02em;
  white-space: nowrap;
  flex-shrink: 0;
}
.nav__logo span { color: var(--clr-accent); }
.nav__logo:hover { text-decoration: none; opacity: .9; }

.nav__list {
  display: none;
  gap: var(--sp-1);
  align-items: center;
}
.nav__list a {
  color: rgba(255,255,255,.85);
  font-size: .9rem;
  font-weight: 500;
  padding: var(--sp-2) var(--sp-3);
  border-radius: var(--radius);
  transition: background var(--transition), color var(--transition);
  white-space: nowrap;
}
.nav__list a:hover { background: rgba(255,255,255,.12); color: #fff; text-decoration: none; }
.nav__list a.active { background: var(--clr-accent); color: #fff; }

.nav__toggle {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 36px;
  height: 36px;
  background: none;
  border: none;
  padding: 0;
  flex-shrink: 0;
}
.nav__toggle span {
  display: block;
  height: 2px;
  background: #fff;
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}
.nav__toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav__toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav__toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

.nav__mobile {
  display: none;
  background: var(--clr-primary);
  border-top: 1px solid rgba(255,255,255,.1);
  padding: var(--sp-4) var(--sp-6);
}
.nav__mobile.open { display: block; }
.nav__mobile a {
  display: block;
  color: rgba(255,255,255,.85);
  padding: var(--sp-3) 0;
  border-bottom: 1px solid rgba(255,255,255,.08);
  font-size: .95rem;
  font-weight: 500;
}
.nav__mobile a:hover { color: #fff; text-decoration: none; }
.nav__mobile a:last-child { border-bottom: none; }

@media (min-width: 900px) {
  .nav__list { display: flex; }
  .nav__toggle { display: none; }
}

/* ---------- Hero ------------------------------------------- */
.hero {
  background: linear-gradient(135deg, var(--clr-primary) 0%, var(--clr-primary-light) 100%);
  color: #fff;
  padding: var(--sp-16) 0 var(--sp-12);
}
.hero--small { padding: var(--sp-12) 0 var(--sp-10); }
.hero__content { max-width: 760px; }
.hero__badge {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-2);
  background: rgba(255,255,255,.15);
  border: 1px solid rgba(255,255,255,.25);
  border-radius: 100px;
  padding: var(--sp-1) var(--sp-3);
  font-size: .8rem;
  font-weight: 600;
  letter-spacing: .04em;
  text-transform: uppercase;
  margin-bottom: var(--sp-4);
}
.hero__title {
  font-size: clamp(1.75rem, 4vw, 2.75rem);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -.03em;
  margin-bottom: var(--sp-4);
}
.hero__title em { font-style: normal; color: var(--clr-accent); }
.hero__subtitle {
  font-size: clamp(1rem, 2vw, 1.2rem);
  color: rgba(255,255,255,.85);
  line-height: 1.6;
  margin-bottom: var(--sp-8);
  max-width: 640px;
}
.hero__ctas { display: flex; gap: var(--sp-3); flex-wrap: wrap; }

/* ---------- Buttons ---------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--sp-2);
  padding: var(--sp-3) var(--sp-6);
  border: 2px solid transparent;
  border-radius: var(--radius);
  font-size: .95rem;
  font-weight: 600;
  line-height: 1;
  cursor: pointer;
  transition: background var(--transition), transform var(--transition), box-shadow var(--transition), border-color var(--transition);
  text-decoration: none;
  white-space: nowrap;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn:active { transform: translateY(0); }
.btn:focus-visible { outline: 2px solid var(--clr-accent); outline-offset: 2px; }

.btn--primary {
  background: var(--clr-accent);
  color: var(--clr-primary);
  border-color: var(--clr-accent);
  box-shadow: var(--shadow-md);
}
.btn--primary:hover { background: #38bdf8; border-color: #38bdf8; color: var(--clr-primary); }

.btn--secondary {
  background: rgba(255,255,255,.15);
  color: #fff;
  border-color: rgba(255,255,255,.4);
}
.btn--secondary:hover { background: rgba(255,255,255,.25); color: #fff; }

.btn--outline {
  background: transparent;
  color: var(--clr-primary-light);
  border-color: var(--clr-primary-light);
}
.btn--outline:hover { background: var(--clr-primary-xlight); color: var(--clr-primary); }

.btn--success {
  background: var(--clr-success);
  color: #fff;
  border-color: var(--clr-success);
}
.btn--success:hover { background: #15803d; }

.btn--large { padding: var(--sp-4) var(--sp-8); font-size: 1.05rem; border-radius: var(--radius-lg); }
.btn--full { width: 100%; }

/* ---------- Sections --------------------------------------- */
.section { padding: var(--sp-16) 0; }
.section--alt { background: var(--clr-bg-alt); }
.section--dark { background: var(--clr-primary); color: #fff; }
.section--sm { padding: var(--sp-10) 0; }

.section__header { margin-bottom: var(--sp-10); }
.section__header--centered { text-align: center; }
.section__label {
  display: inline-block;
  font-size: .8rem;
  font-weight: 700;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--clr-primary-light);
  margin-bottom: var(--sp-3);
}
.section--dark .section__label { color: var(--clr-accent-light); }
.section__title {
  font-size: clamp(1.5rem, 3vw, 2.25rem);
  font-weight: 800;
  letter-spacing: -.025em;
  line-height: 1.2;
  color: var(--clr-primary);
  margin-bottom: var(--sp-3);
}
.section--dark .section__title { color: #fff; }
.section__subtitle {
  font-size: 1.05rem;
  color: var(--clr-text-muted);
  line-height: 1.6;
  max-width: 640px;
}
.section--dark .section__subtitle { color: rgba(255,255,255,.75); }

/* ---------- Tool Card -------------------------------------- */
.tool-card {
  background: var(--clr-bg);
  border: 2px solid var(--clr-border);
  border-radius: var(--radius-xl);
  padding: var(--sp-8);
  box-shadow: var(--shadow-lg);
}
.tool-card__title {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--clr-primary);
  margin-bottom: var(--sp-2);
}
.tool-card__desc {
  color: var(--clr-text-muted);
  font-size: .95rem;
  margin-bottom: var(--sp-6);
}

/* Form elements */
.form-group { margin-bottom: var(--sp-4); }
.form-label {
  display: block;
  font-size: .9rem;
  font-weight: 600;
  color: var(--clr-neutral-700);
  margin-bottom: var(--sp-2);
}
.form-input {
  display: block;
  width: 100%;
  padding: var(--sp-3) var(--sp-4);
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--clr-text);
  background: var(--clr-bg);
  border: 2px solid var(--clr-border);
  border-radius: var(--radius-lg);
  transition: border-color var(--transition), box-shadow var(--transition);
  -webkit-appearance: none;
}
.form-input:focus {
  outline: none;
  border-color: var(--clr-accent);
  box-shadow: 0 0 0 3px rgba(14,165,233,.15);
}
.form-input--large { font-size: 1.5rem; padding: var(--sp-4) var(--sp-5); }
.form-input::placeholder { color: var(--clr-neutral-400); font-weight: 400; }
.form-error { font-size: .85rem; color: var(--clr-error); margin-top: var(--sp-2); display: none; }
.form-error.visible { display: block; }

/* Tool Actions */
.tool-actions { display: flex; gap: var(--sp-3); flex-wrap: wrap; margin-top: var(--sp-4); }

/* Result Box */
.result-box {
  margin-top: var(--sp-6);
  border-radius: var(--radius-lg);
  padding: var(--sp-6);
  border: 2px solid transparent;
  display: none;
}
.result-box.visible { display: block; }
.result-box--prime {
  background: var(--clr-success-light);
  border-color: var(--clr-success);
}
.result-box--not-prime {
  background: var(--clr-warning-light);
  border-color: var(--clr-warning);
}
.result-box--info {
  background: var(--clr-primary-xlight);
  border-color: var(--clr-accent);
}
.result-box--error {
  background: var(--clr-error-light);
  border-color: var(--clr-error);
}
.result-box__verdict {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  margin-bottom: var(--sp-4);
}
.result-box__icon {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  flex-shrink: 0;
}
.result-box--prime .result-box__icon { background: var(--clr-success); color: #fff; }
.result-box--not-prime .result-box__icon { background: var(--clr-warning); color: #fff; }
.result-box__number { font-size: 1.5rem; font-weight: 800; color: var(--clr-primary); }
.result-box__label { font-size: 1rem; font-weight: 600; }
.result-box--prime .result-box__label { color: var(--clr-success); }
.result-box--not-prime .result-box__label { color: var(--clr-warning); }

.result-details { display: grid; gap: var(--sp-3); }
.result-detail {
  display: flex;
  gap: var(--sp-3);
  align-items: flex-start;
  background: rgba(255,255,255,.6);
  border-radius: var(--radius);
  padding: var(--sp-3) var(--sp-4);
}
.result-detail__label {
  font-size: .85rem;
  font-weight: 700;
  color: var(--clr-text-muted);
  min-width: 180px;
  flex-shrink: 0;
}
.result-detail__value { font-size: .95rem; font-weight: 600; color: var(--clr-text); }
@media (max-width: 480px) {
  .result-detail { flex-direction: column; gap: var(--sp-1); }
  .result-detail__label { min-width: unset; }
}

/* ---------- Cards ------------------------------------------ */
.card {
  background: var(--clr-bg);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-lg);
  padding: var(--sp-6);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), transform var(--transition);
}
.card:hover { box-shadow: var(--shadow-md); transform: translateY(-2px); }
.card__icon {
  width: 48px;
  height: 48px;
  background: var(--clr-primary-xlight);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  margin-bottom: var(--sp-4);
}
.card__title {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--clr-primary);
  margin-bottom: var(--sp-2);
}
.card__desc { font-size: .9rem; color: var(--clr-text-muted); line-height: 1.6; }
.card__link {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-1);
  margin-top: var(--sp-4);
  font-size: .9rem;
  font-weight: 600;
  color: var(--clr-primary-light);
}
.card__link:hover { text-decoration: underline; }

/* ---------- Grids ------------------------------------------ */
.grid { display: grid; gap: var(--sp-6); }
.grid--2 { grid-template-columns: 1fr; }
.grid--3 { grid-template-columns: 1fr; }
.grid--4 { grid-template-columns: 1fr; }
@media (min-width: 600px) {
  .grid--2 { grid-template-columns: repeat(2, 1fr); }
  .grid--4 { grid-template-columns: repeat(2, 1fr); }
}
@media (min-width: 768px) {
  .grid--3 { grid-template-columns: repeat(3, 1fr); }
}
@media (min-width: 900px) {
  .grid--4 { grid-template-columns: repeat(4, 1fr); }
}

/* ---------- Tables ----------------------------------------- */
.table-responsive { overflow-x: auto; -webkit-overflow-scrolling: touch; border-radius: var(--radius-lg); border: 1px solid var(--clr-border); }
table th, table td {
  padding: var(--sp-3) var(--sp-4);
  text-align: left;
  border-bottom: 1px solid var(--clr-border);
  font-size: .9rem;
}
table th {
  background: var(--clr-primary);
  color: #fff;
  font-weight: 700;
  font-size: .85rem;
  letter-spacing: .03em;
  text-transform: uppercase;
}
table tr:last-child td { border-bottom: none; }
table tbody tr:nth-child(even) { background: var(--clr-neutral-50); }
table tbody tr:hover { background: var(--clr-primary-xlight); }
.cell--prime { font-weight: 700; color: var(--clr-success); }
.cell--composite { color: var(--clr-text-muted); }

/* ---------- Number Grid (Primzahlen Gitter) ---------------- */
.number-grid {
  display: grid;
  grid-template-columns: repeat(10, 1fr);
  gap: var(--sp-2);
  margin: var(--sp-6) 0;
}
.number-cell {
  aspect-ratio: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: .85rem;
  font-weight: 600;
  border-radius: var(--radius);
  border: 1px solid var(--clr-border);
  background: var(--clr-bg);
  transition: background var(--transition);
}
.number-cell--prime {
  background: var(--clr-primary);
  color: #fff;
  border-color: var(--clr-primary);
}
.number-cell--one {
  background: var(--clr-neutral-200);
  color: var(--clr-text-muted);
}
@media (max-width: 480px) { .number-cell { font-size: .75rem; } }

/* ---------- FAQ -------------------------------------------- */
.faq-list { display: flex; flex-direction: column; gap: var(--sp-3); }
.faq-item {
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.faq-question {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-4);
  width: 100%;
  background: none;
  border: none;
  padding: var(--sp-4) var(--sp-5);
  text-align: left;
  font-size: .95rem;
  font-weight: 600;
  color: var(--clr-primary);
  cursor: pointer;
  transition: background var(--transition);
}
.faq-question:hover { background: var(--clr-neutral-50); }
.faq-question[aria-expanded="true"] { background: var(--clr-primary-xlight); }
.faq-question__icon {
  flex-shrink: 0;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--clr-primary);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: .9rem;
  transition: transform var(--transition);
}
.faq-question[aria-expanded="true"] .faq-question__icon { transform: rotate(45deg); background: var(--clr-accent); }
.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height .3s ease;
}
.faq-answer__inner {
  padding: 0 var(--sp-5) var(--sp-5);
  font-size: .95rem;
  color: var(--clr-text);
  line-height: 1.7;
  border-top: 1px solid var(--clr-border);
  padding-top: var(--sp-4);
}
.faq-answer__inner p + p { margin-top: var(--sp-3); }
.faq-answer__inner ul { list-style: disc; padding-left: var(--sp-5); }
.faq-answer__inner li { margin-bottom: var(--sp-1); }

/* ---------- Steps ------------------------------------------ */
.steps { counter-reset: step; display: flex; flex-direction: column; gap: var(--sp-4); }
.step {
  display: flex;
  gap: var(--sp-4);
  align-items: flex-start;
}
.step__number {
  counter-increment: step;
  flex-shrink: 0;
  width: 40px;
  height: 40px;
  background: var(--clr-primary);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: .95rem;
}
.step__content { flex: 1; }
.step__title { font-weight: 700; color: var(--clr-primary); margin-bottom: var(--sp-1); }
.step__desc { color: var(--clr-text-muted); font-size: .95rem; line-height: 1.6; }

/* ---------- Highlight Box ---------------------------------- */
.highlight-box {
  background: var(--clr-primary-xlight);
  border-left: 4px solid var(--clr-primary-light);
  border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
  padding: var(--sp-5) var(--sp-6);
  margin: var(--sp-6) 0;
}
.highlight-box--success {
  background: var(--clr-success-light);
  border-color: var(--clr-success);
}
.highlight-box--warning {
  background: var(--clr-warning-light);
  border-color: var(--clr-warning);
}
.highlight-box__title {
  font-weight: 700;
  color: var(--clr-primary);
  margin-bottom: var(--sp-2);
}
.highlight-box p { font-size: .95rem; line-height: 1.6; margin: 0; }

/* ---------- Breadcrumb ------------------------------------- */
.breadcrumb {
  padding: var(--sp-3) 0;
  font-size: .85rem;
  color: var(--clr-text-muted);
}
.breadcrumb ol { display: flex; flex-wrap: wrap; gap: var(--sp-1); align-items: center; }
.breadcrumb li { display: flex; align-items: center; gap: var(--sp-1); }
.breadcrumb li:not(:last-child)::after { content: "›"; color: var(--clr-neutral-400); }
.breadcrumb a { color: var(--clr-text-muted); }
.breadcrumb a:hover { color: var(--clr-primary-light); }
.breadcrumb [aria-current="page"] { color: var(--clr-text); font-weight: 600; }
.breadcrumb span { color: var(--clr-neutral-400); }
.breadcrumb > .container { display: flex; flex-wrap: wrap; align-items: center; gap: var(--sp-2); }

/* ---------- Author Box ------------------------------------- */
.author-box {
  display: flex;
  gap: var(--sp-4);
  align-items: flex-start;
  background: var(--clr-bg-alt);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-lg);
  padding: var(--sp-5) var(--sp-6);
  margin-top: var(--sp-10);
}
.author-box__avatar {
  width: 56px;
  height: 56px;
  background: var(--clr-primary);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 1.5rem;
  flex-shrink: 0;
}
.author-box__name { font-weight: 700; color: var(--clr-primary); margin-bottom: var(--sp-1); }
.author-box__desc { font-size: .9rem; color: var(--clr-text-muted); line-height: 1.6; }
.author-box__updated { font-size: .8rem; color: var(--clr-neutral-400); margin-top: var(--sp-1); }

/* ---------- Badges ----------------------------------------- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-1);
  padding: var(--sp-1) var(--sp-3);
  border-radius: 100px;
  font-size: .8rem;
  font-weight: 700;
  letter-spacing: .03em;
}
.badge--prime { background: var(--clr-success); color: #fff; }
.badge--composite { background: var(--clr-warning-light); color: var(--clr-warning); border: 1px solid var(--clr-warning); }
.badge--info { background: var(--clr-accent-light); color: var(--clr-primary); }
.badge--neutral { background: var(--clr-neutral-200); color: var(--clr-neutral-700); }

/* ---------- Alert ------------------------------------------ */
.alert {
  display: flex;
  gap: var(--sp-3);
  align-items: flex-start;
  padding: var(--sp-4) var(--sp-5);
  border-radius: var(--radius-lg);
  font-size: .95rem;
  line-height: 1.6;
}
.alert--success { background: var(--clr-success-light); color: #14532d; }
.alert--warning { background: var(--clr-warning-light); color: #7c2d12; }
.alert--error   { background: var(--clr-error-light);   color: #7f1d1d; }
.alert--info    { background: var(--clr-primary-xlight); color: var(--clr-primary); }
.alert__icon { font-size: 1.2rem; flex-shrink: 0; }

/* ---------- Primfaktor Display ----------------------------- */
.factorization {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--clr-primary);
  margin: var(--sp-4) 0;
  line-height: 1.4;
}
.factorization .factor { color: var(--clr-success); }
.factorization .factor-sep { color: var(--clr-text-muted); margin: 0 .1em; }
.factor-tree {
  display: flex;
  flex-direction: column;
  gap: var(--sp-2);
  margin: var(--sp-4) 0;
  font-size: .95rem;
}
.factor-tree-row {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  padding: var(--sp-2) var(--sp-3);
  background: var(--clr-neutral-50);
  border-radius: var(--radius);
}

/* ---------- Number Tag List -------------------------------- */
.tag-cloud { display: flex; flex-wrap: wrap; gap: var(--sp-2); margin: var(--sp-4) 0; }
.num-tag {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 44px;
  padding: var(--sp-2) var(--sp-3);
  background: var(--clr-primary);
  color: #fff;
  border-radius: var(--radius);
  font-size: .9rem;
  font-weight: 700;
  transition: background var(--transition);
}
.num-tag:hover { background: var(--clr-primary-light); }

/* ---------- Stats / Feature Rows --------------------------- */
.stats-row { display: grid; grid-template-columns: repeat(2, 1fr); gap: var(--sp-4); }
@media (min-width: 600px) { .stats-row { grid-template-columns: repeat(4, 1fr); } }
.stat-card {
  background: rgba(255,255,255,.1);
  border: 1px solid rgba(255,255,255,.2);
  border-radius: var(--radius-lg);
  padding: var(--sp-5);
  text-align: center;
}
.stat-card__value {
  font-size: 2rem;
  font-weight: 800;
  color: var(--clr-accent);
  line-height: 1;
  margin-bottom: var(--sp-2);
}
.stat-card__label {
  font-size: .85rem;
  color: rgba(255,255,255,.75);
}

/* ---------- Definition Box --------------------------------- */
.definition-box {
  border: 2px solid var(--clr-primary);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin: var(--sp-6) 0;
}
.definition-box__header {
  background: var(--clr-primary);
  color: #fff;
  padding: var(--sp-3) var(--sp-5);
  font-size: .85rem;
  font-weight: 700;
  letter-spacing: .05em;
  text-transform: uppercase;
}
.definition-box__body {
  padding: var(--sp-5) var(--sp-6);
  font-size: 1rem;
  line-height: 1.7;
}
.definition-box__body strong { color: var(--clr-primary); }

/* ---------- Sieb des Eratosthenes Grid --------------------- */
.sieve-grid {
  display: grid;
  grid-template-columns: repeat(10, 1fr);
  gap: 3px;
  margin: var(--sp-6) 0;
}
.sieve-cell {
  aspect-ratio: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: .8rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  border: 1px solid var(--clr-border);
  background: var(--clr-bg);
  transition: background .2s, color .2s;
}
.sieve-cell--current { background: var(--clr-accent); color: #fff; border-color: var(--clr-accent); }
.sieve-cell--prime { background: var(--clr-primary); color: #fff; border-color: var(--clr-primary); }
.sieve-cell--composite { background: var(--clr-neutral-200); color: var(--clr-neutral-400); text-decoration: line-through; }
.sieve-cell--one { background: var(--clr-neutral-100); color: var(--clr-neutral-400); }
@media (max-width: 480px) { .sieve-cell { font-size: .65rem; } }

/* ---------- Quiz ------------------------------------------- */
.quiz-card {
  background: var(--clr-bg);
  border: 2px solid var(--clr-border);
  border-radius: var(--radius-xl);
  padding: var(--sp-8);
  box-shadow: var(--shadow-lg);
}
.quiz-question {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--clr-primary);
  margin-bottom: var(--sp-6);
  line-height: 1.4;
}
.quiz-options { display: flex; flex-direction: column; gap: var(--sp-3); margin-bottom: var(--sp-6); }
.quiz-option {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  padding: var(--sp-4);
  border: 2px solid var(--clr-border);
  border-radius: var(--radius-lg);
  background: var(--clr-bg);
  cursor: pointer;
  transition: border-color var(--transition), background var(--transition);
  font-size: .95rem;
  font-weight: 500;
  color: var(--clr-text);
  text-align: left;
  width: 100%;
}
.quiz-option:hover { border-color: var(--clr-primary-light); background: var(--clr-primary-xlight); }
.quiz-option--correct { border-color: var(--clr-success); background: var(--clr-success-light); color: #14532d; }
.quiz-option--wrong   { border-color: var(--clr-error);   background: var(--clr-error-light);   color: #7f1d1d; }
.quiz-option--disabled { pointer-events: none; opacity: .7; }
.quiz-option__marker {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  border: 2px solid var(--clr-border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: .85rem;
  flex-shrink: 0;
}
.quiz-feedback {
  padding: var(--sp-4) var(--sp-5);
  border-radius: var(--radius-lg);
  font-size: .95rem;
  line-height: 1.6;
  display: none;
}
.quiz-feedback.visible { display: block; }
.quiz-feedback--correct { background: var(--clr-success-light); color: #14532d; }
.quiz-feedback--wrong   { background: var(--clr-error-light);   color: #7f1d1d; }
.quiz-progress {
  font-size: .85rem;
  color: var(--clr-text-muted);
  margin-bottom: var(--sp-4);
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.quiz-progress-bar {
  height: 4px;
  background: var(--clr-border);
  border-radius: 2px;
  overflow: hidden;
  margin-bottom: var(--sp-6);
}
.quiz-progress-bar__fill {
  height: 100%;
  background: var(--clr-primary);
  border-radius: 2px;
  transition: width .3s ease;
}
.quiz-score {
  text-align: center;
  padding: var(--sp-8);
}
.quiz-score__value {
  font-size: 3rem;
  font-weight: 800;
  color: var(--clr-primary);
  line-height: 1;
  margin-bottom: var(--sp-3);
}
.quiz-score__label { font-size: 1.1rem; color: var(--clr-text-muted); margin-bottom: var(--sp-6); }

/* ---------- Newsletter CTA --------------------------------- */
.newsletter {
  background: var(--clr-primary);
  color: #fff;
  border-radius: var(--radius-xl);
  padding: var(--sp-10) var(--sp-8);
  text-align: center;
}
.newsletter__title { font-size: 1.5rem; font-weight: 800; margin-bottom: var(--sp-3); }
.newsletter__desc { color: rgba(255,255,255,.8); margin-bottom: var(--sp-6); }
.newsletter__form { display: flex; gap: var(--sp-3); max-width: 480px; margin-inline: auto; flex-wrap: wrap; }
.newsletter__input {
  flex: 1;
  min-width: 200px;
  padding: var(--sp-3) var(--sp-4);
  border: 2px solid rgba(255,255,255,.3);
  border-radius: var(--radius-lg);
  background: rgba(255,255,255,.1);
  color: #fff;
  font-size: .95rem;
}
.newsletter__input::placeholder { color: rgba(255,255,255,.5); }
.newsletter__input:focus { outline: none; border-color: var(--clr-accent); }

/* ---------- Footer ----------------------------------------- */
.footer {
  background: var(--clr-neutral-900);
  color: rgba(255,255,255,.8);
}
.footer__inner {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--sp-10);
  padding: var(--sp-16) 0 var(--sp-12);
}
@media (min-width: 640px)  { .footer__inner { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 1024px) { .footer__inner { grid-template-columns: 2fr 1fr 1fr 1fr 1fr; } }
.footer__brand .nav__logo { color: #fff; font-size: 1.3rem; }
.footer__brand p { font-size: .9rem; color: rgba(255,255,255,.55); line-height: 1.6; margin-top: var(--sp-3); max-width: 280px; }
.footer__links h3 { font-size: .85rem; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; color: rgba(255,255,255,.4); margin-bottom: var(--sp-4); }
.footer__links ul { display: flex; flex-direction: column; gap: var(--sp-3); }
.footer__links a { color: rgba(255,255,255,.7); font-size: .9rem; transition: color var(--transition); }
.footer__links a:hover { color: #fff; text-decoration: none; }
.footer__bottom {
  border-top: 1px solid rgba(255,255,255,.08);
  padding: var(--sp-5) 0;
  font-size: .85rem;
  color: rgba(255,255,255,.4);
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: var(--sp-3);
  align-items: center;
}
.footer__bottom a { color: rgba(255,255,255,.5); }
.footer__bottom a:hover { color: rgba(255,255,255,.8); text-decoration: none; }

/* ---------- Article Layout --------------------------------- */
.article-layout {
  display: grid;
  gap: var(--sp-12);
  grid-template-columns: 1fr;
}
@media (min-width: 1024px) { .article-layout { grid-template-columns: 1fr 320px; } }
.article-content h2 {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--clr-primary);
  letter-spacing: -.025em;
  margin: var(--sp-10) 0 var(--sp-4);
  padding-top: var(--sp-8);
  border-top: 2px solid var(--clr-border);
}
.article-content h2:first-of-type { margin-top: 0; border-top: none; padding-top: 0; }
.article-content h3 {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--clr-primary);
  margin: var(--sp-6) 0 var(--sp-3);
}
.article-content p { margin-bottom: var(--sp-4); line-height: 1.7; }
.article-content ul, .article-content ol {
  padding-left: var(--sp-5);
  margin-bottom: var(--sp-4);
}
.article-content ul { list-style: disc; }
.article-content ol { list-style: decimal; }
.article-content li { margin-bottom: var(--sp-2); line-height: 1.6; }
.article-content strong { color: var(--clr-primary); }
.article-content em { font-style: italic; }

/* TOC (Inhaltsverzeichnis) */
.toc {
  background: var(--clr-bg-alt);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-lg);
  padding: var(--sp-5);
  margin-bottom: var(--sp-8);
}
.toc__title { font-weight: 700; color: var(--clr-primary); margin-bottom: var(--sp-3); font-size: .95rem; }
.toc ol { counter-reset: toc; list-style: none; padding: 0; }
.toc li { counter-increment: toc; margin-bottom: var(--sp-2); }
.toc a { font-size: .9rem; color: var(--clr-text-muted); }
.toc a:hover { color: var(--clr-primary-light); }

/* Sidebar */
.sidebar { display: flex; flex-direction: column; gap: var(--sp-6); }
.sidebar-widget {
  background: var(--clr-bg-alt);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-lg);
  padding: var(--sp-5);
}
.sidebar-widget__title { font-size: .95rem; font-weight: 700; color: var(--clr-primary); margin-bottom: var(--sp-4); }
.sidebar-widget a {
  display: block;
  color: var(--clr-text-muted);
  font-size: .9rem;
  padding: var(--sp-2) 0;
  border-bottom: 1px solid var(--clr-border);
}
.sidebar-widget a:hover { color: var(--clr-primary-light); text-decoration: none; }
.sidebar-widget a:last-child { border-bottom: none; }

/* ---------- Übungen ---------------------------------------- */
.exercise {
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin-bottom: var(--sp-4);
}
.exercise__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--sp-4) var(--sp-5);
  background: var(--clr-neutral-50);
  gap: var(--sp-4);
}
.exercise__num {
  width: 32px;
  height: 32px;
  background: var(--clr-primary);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: .85rem;
  font-weight: 700;
  flex-shrink: 0;
}
.exercise__question { flex: 1; font-weight: 600; color: var(--clr-primary); }
.exercise__toggle {
  background: none;
  border: 1px solid var(--clr-border);
  border-radius: var(--radius);
  padding: var(--sp-2) var(--sp-3);
  font-size: .8rem;
  font-weight: 600;
  color: var(--clr-text-muted);
  cursor: pointer;
  white-space: nowrap;
}
.exercise__toggle:hover { background: var(--clr-primary-xlight); color: var(--clr-primary); }
.exercise__solution {
  max-height: 0;
  overflow: hidden;
  transition: max-height .3s ease;
}
.exercise__solution.open { max-height: 500px; }
.exercise__solution-inner {
  padding: var(--sp-4) var(--sp-5);
  border-top: 1px solid var(--clr-border);
  background: var(--clr-success-light);
  font-size: .95rem;
  line-height: 1.6;
  color: #14532d;
}

/* ---------- Kopier-Button ---------------------------------- */
.copy-box {
  display: flex;
  align-items: flex-start;
  gap: var(--sp-3);
  margin: var(--sp-6) 0;
}
.copy-box__content {
  flex: 1;
  background: var(--clr-neutral-900);
  color: var(--clr-neutral-200);
  border-radius: var(--radius-lg);
  padding: var(--sp-4) var(--sp-5);
  font-family: var(--font-mono);
  font-size: .85rem;
  line-height: 1.6;
  overflow-x: auto;
  max-height: 300px;
  overflow-y: auto;
}
.copy-btn {
  flex-shrink: 0;
  padding: var(--sp-3) var(--sp-4);
  background: var(--clr-primary);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: .85rem;
  font-weight: 600;
  cursor: pointer;
  transition: background var(--transition);
}
.copy-btn:hover { background: var(--clr-primary-light); }
.copy-btn--success { background: var(--clr-success); }

/* ---------- Utility Classes -------------------------------- */
.text-center { text-align: center; }
.text-muted { color: var(--clr-text-muted); }
.text-success { color: var(--clr-success); }
.text-warning { color: var(--clr-warning); }
.text-primary { color: var(--clr-primary); }
.font-bold { font-weight: 700; }
.font-mono { font-family: var(--font-mono); }
.mt-4 { margin-top: var(--sp-4); }
.mt-6 { margin-top: var(--sp-6); }
.mt-8 { margin-top: var(--sp-8); }
.mb-4 { margin-bottom: var(--sp-4); }
.mb-6 { margin-bottom: var(--sp-6); }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
.visually-hidden { @extend .sr-only; }

/* ---------- Animations ------------------------------------- */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}
.animate-fade-in-up { animation: fadeInUp .4s ease both; }
.animate-delay-1 { animation-delay: .1s; }
.animate-delay-2 { animation-delay: .2s; }
.animate-delay-3 { animation-delay: .3s; }

/* ---------- Übungs-Alternative Klassen (aus uebungen.html) - */
.exercise__question {
  font-weight: 600;
  color: var(--clr-primary);
  padding: var(--sp-4) var(--sp-5);
  background: var(--clr-neutral-50);
  border-bottom: 1px solid var(--clr-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-3);
  cursor: pointer;
  user-select: none;
}
.exercise__question:hover { background: var(--clr-primary-xlight); }
.exercise__answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height .3s ease;
  background: var(--clr-success-light);
}
.exercise__answer.open { max-height: 600px; }
.exercise__answer p { padding: var(--sp-4) var(--sp-5); color: #14532d; font-size: .95rem; line-height: 1.6; margin: 0; border-top: 1px solid var(--clr-border); }
.exercise__answer p + p { border-top: none; padding-top: 0; }

/* ---------- Print ------------------------------------------ */
@media print {
  .nav, .footer, .newsletter, .hero__ctas { display: none; }
  body { font-size: 12pt; }
  .container { max-width: 100%; padding: 0; }
}