@import url("https://fonts.googleapis.com/css2?family=IBM+Plex+Sans:wght@300;400;600&family=IBM+Plex+Serif:wght@400;600&display=swap");

:root {
  --bg: #f6f0e6;
  --ink: #1f1b16;
  --ink-soft: #5d534a;
  --accent: #c24b2c;
  --accent-2: #225b5f;
  --panel: #fff8f0;
  --panel-edge: rgba(31, 27, 22, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "IBM Plex Sans", "Helvetica Neue", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at 10% 15%, rgba(194, 75, 44, 0.12), transparent 45%),
    radial-gradient(circle at 85% 20%, rgba(34, 91, 95, 0.15), transparent 55%),
    linear-gradient(135deg, #fefaf4 0%, #f3e8d8 100%);
  min-height: 100vh;
}

.bg-glow {
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(0, 0, 0, 0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0, 0, 0, 0.05) 1px, transparent 1px);
  background-size: 40px 40px;
  opacity: 0.15;
  pointer-events: none;
  z-index: 0;
}

header.hero {
  position: relative;
  padding: 72px 10vw 36px;
  z-index: 1;
}

.hero-inner {
  max-width: 900px;
}

.eyebrow {
  font-family: "IBM Plex Serif", "Times New Roman", serif;
  text-transform: uppercase;
  letter-spacing: 0.3em;
  color: var(--accent-2);
  margin: 0 0 16px;
  font-size: 0.75rem;
}

h1 {
  font-family: "IBM Plex Serif", "Times New Roman", serif;
  font-size: clamp(2.4rem, 5vw, 4.2rem);
  margin: 0 0 16px;
}

.subtitle {
  font-size: 1.1rem;
  color: var(--ink-soft);
  max-width: 620px;
  line-height: 1.6;
}

.top-bar {
  margin-top: 28px;
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  align-items: center;
  justify-content: space-between;
}

.tabs {
  display: inline-flex;
  gap: 8px;
  background: rgba(31, 27, 22, 0.05);
  padding: 6px;
  border-radius: 999px;
  border: 1px solid rgba(31, 27, 22, 0.08);
}

.tab {
  border: none;
  background: transparent;
  padding: 10px 16px;
  border-radius: 999px;
  font-weight: 600;
  color: var(--ink-soft);
  cursor: pointer;
}

.tab.active {
  background: #fff;
  color: var(--ink);
  box-shadow: 0 6px 14px rgba(31, 27, 22, 0.12);
}

.lang-toggle {
  display: inline-flex;
  gap: 6px;
  padding: 6px;
  border-radius: 999px;
  border: 1px solid rgba(31, 27, 22, 0.08);
  background: rgba(31, 27, 22, 0.05);
}

.lang-btn {
  border: none;
  background: transparent;
  padding: 8px 14px;
  border-radius: 999px;
  font-weight: 600;
  cursor: pointer;
  color: var(--ink-soft);
}

.lang-btn.active {
  background: #fff;
  color: var(--ink);
  box-shadow: 0 6px 14px rgba(31, 27, 22, 0.12);
}

main {
  padding: 0 10vw 80px;
  display: grid;
  gap: 32px;
  position: relative;
  z-index: 1;
}

.panel {
  background: var(--panel);
  border-radius: 24px;
  box-shadow: 0 20px 40px rgba(31, 27, 22, 0.08);
  border: 1px solid var(--panel-edge);
  padding: 28px clamp(24px, 4vw, 48px);
  animation: fadeUp 0.8s ease both;
}

.panel:nth-of-type(2) {
  animation-delay: 0.15s;
}

.tab-panel {
  display: none;
}

.tab-panel.active {
  display: block;
}

.panel-head h2 {
  margin: 0 0 8px;
  font-size: 1.8rem;
}

.panel-head p {
  margin: 0 0 20px;
  color: var(--ink-soft);
}

.checker label {
  font-weight: 600;
  display: block;
  margin-bottom: 8px;
}

.input-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 12px;
  align-items: center;
}

input#n-input {
  padding: 14px 16px;
  border: 1px solid rgba(31, 27, 22, 0.15);
  border-radius: 12px;
  font-size: 1rem;
  background: #fff;
}

button#check-btn {
  padding: 14px 20px;
  border-radius: 12px;
  border: none;
  background: var(--accent);
  color: #fff;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

button#check-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 20px rgba(194, 75, 44, 0.25);
}

.result {
  margin-top: 20px;
  padding: 18px 20px;
  border-radius: 16px;
  border: 1px dashed rgba(31, 27, 22, 0.2);
  background: rgba(255, 255, 255, 0.7);
}

.result-title {
  font-weight: 700;
  margin-bottom: 6px;
}

.result.good {
  border-color: rgba(34, 91, 95, 0.5);
  background: rgba(34, 91, 95, 0.1);
}

.result.bad {
  border-color: rgba(194, 75, 44, 0.6);
  background: rgba(194, 75, 44, 0.1);
}

.steps {
  margin-top: 24px;
  background: rgba(34, 91, 95, 0.08);
  padding: 16px 20px;
  border-radius: 14px;
}

.steps-title {
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--accent-2);
}

ol {
  margin: 0 0 0 18px;
  padding: 0;
}

.markdown h1,
.markdown h2,
.markdown h3 {
  font-family: "IBM Plex Serif", "Times New Roman", serif;
  margin: 24px 0 8px;
}

.markdown p {
  line-height: 1.7;
  margin: 12px 0;
  color: var(--ink-soft);
}

.markdown ul {
  margin: 12px 0 12px 20px;
}

.markdown code {
  background: rgba(31, 27, 22, 0.08);
  padding: 2px 6px;
  border-radius: 6px;
  font-family: "IBM Plex Mono", "Courier New", monospace;
  font-size: 0.95em;
}

.markdown pre {
  background: #1f1b16;
  color: #f6f0e6;
  padding: 16px;
  border-radius: 12px;
  overflow-x: auto;
}

footer {
  padding: 20px 10vw 40px;
  color: var(--ink-soft);
  font-size: 0.9rem;
}

@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(16px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (max-width: 700px) {
  header.hero {
    padding: 56px 6vw 24px;
  }

  main {
    padding: 0 6vw 60px;
  }

  .input-row {
    grid-template-columns: 1fr;
  }

  button#check-btn {
    width: 100%;
  }
}