:root {
  /* Dark-theme variant of the colinstiles.com brand palette
     (olive green / saddle brown / cream) on a true dark background. */
  --primary-color: #9CBB74; /* Lightened Dark Olive Green, for contrast on dark bg */
  --primary-color-rgb: 156, 187, 116;
  --secondary-color: #D99A5B; /* Lightened Saddle Brown */
  --text-color: #F2EFE4; /* Beige/cream */
  --text-color-muted: #B8B5A8;
  --background-page: #15150F; /* Near-black, warm undertone */
  --background-panel: #1E2017;
  --background-panel-hover: #262819;
  --border-color: #3A3B2D;

  --font-family-base: 'Lato', sans-serif;
  --font-size-base: 17px;
  --font-size-small: 0.9em;
  --font-weight-light: 300;
  --font-weight-bold: 900;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  background: var(--background-page);
  color: var(--text-color);
}

a {
  color: var(--primary-color);
}

.challenge-shell {
  max-width: 1440px;
  margin: 0 auto;
  padding: 40px 18px 56px;
}

.challenge-header {
  margin-bottom: 28px;
}

.challenge-back {
  color: var(--text-color-muted);
  font-size: var(--font-size-small);
  text-decoration: none;
}

.challenge-back:hover {
  color: var(--primary-color);
}

.challenge-header h1 {
  margin: 8px 0 8px;
  font-size: 2.2em;
  font-weight: var(--font-weight-light);
  color: var(--primary-color);
}

.challenge-header p {
  margin: 0 0 20px;
  color: var(--text-color-muted);
  max-width: 70ch;
}

.challenge-header a.plan-link {
  color: var(--secondary-color);
  font-size: var(--font-size-small);
}

.year-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 16px;
}

.year-tabs a {
  padding: 8px 16px;
  border-radius: 4px;
  background: var(--background-panel);
  color: var(--primary-color);
  border: 1px solid var(--primary-color);
  font-size: var(--font-size-small);
  text-decoration: none;
  transition: background-color 0.2s ease, color 0.2s ease;
}

.year-tabs a:hover {
  background: var(--primary-color);
  color: var(--background-page);
}

.year-tabs a.active {
  background: var(--primary-color);
  color: var(--background-page);
}

.day-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 22px;
  margin-top: 28px;
}

.day-card {
  background: var(--background-panel);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  overflow: hidden;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background-color 0.2s ease;
}

.day-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 16px rgba(0, 0, 0, 0.35);
  background: var(--background-panel-hover);
}

.day-frame {
  display: block;
  aspect-ratio: 4 / 3;
  background: #0E0E0A;
}

.day-frame img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.day-frame--placeholder {
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 16px;
}

.day-placeholder-text {
  color: var(--text-color-muted);
  font-size: var(--font-size-small);
  font-style: italic;
}

.day-meta {
  padding: 14px 16px 18px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.day-number {
  color: var(--secondary-color);
  font-weight: var(--font-weight-bold);
  font-size: var(--font-size-small);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.day-theme {
  color: var(--text-color-muted);
  font-size: var(--font-size-small);
}

.day-concept {
  margin: 4px 0 2px;
  font-size: 1.05em;
  font-weight: var(--font-weight-light);
  color: var(--text-color);
}

.day-date {
  color: var(--text-color-muted);
  font-size: var(--font-size-small);
}

.day-frame--globe {
  aspect-ratio: 1 / 1;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--background-page);
}

.mars-globe {
  position: relative;
  width: 78%;
  aspect-ratio: 1 / 1;
  border-radius: 50%;
  cursor: grab;
  touch-action: none;
  background: radial-gradient(circle at 35% 30%, #d9d4c7, #6f6a60 70%, #2b2925 100%);
}

.mars-globe:active {
  cursor: grabbing;
}

.mars-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border-radius: 50%;
}

.mars-label {
  position: absolute;
  left: 50%;
  bottom: -26px;
  transform: translateX(-50%);
  color: var(--text-color-muted);
  font-size: var(--font-size-small);
  pointer-events: none;
}

@media (max-width: 600px) {
  .challenge-shell {
    padding: 24px 14px 40px;
  }

  .day-grid {
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 16px;
  }
}