:root {
  --bg: #fbf3e9;          /* kem ấm */
  --bg-soft: #fff8f0;
  --ink: #4a3b34;          /* nâu mực mềm */
  --ink-soft: #8a7a70;
  --clay: #d98c6a;         /* đất nung */
  --clay-dark: #c5765a;
  --sage: #9bb89a;         /* xanh dịu */
  --rose: #e8c1c1;
  --card: #ffffff;
  --shadow: 0 10px 30px rgba(120, 90, 70, 0.10);
  --radius: 22px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: 'Nunito', system-ui, sans-serif;
  color: var(--ink);
  background:
    radial-gradient(1200px 500px at 80% -10%, #ffe9d6 0%, transparent 60%),
    radial-gradient(900px 500px at -10% 20%, #eef3e8 0%, transparent 55%),
    var(--bg);
  line-height: 1.6;
}

h1, h2, h3, .logo, .clock {
  font-family: 'Quicksand', 'Nunito', sans-serif;
}

.site-header {
  display: flex; align-items: center; justify-content: space-between;
  max-width: 920px; margin: 0 auto; padding: 22px 20px;
}
.logo { font-size: 1.3rem; font-weight: 700; color: var(--clay-dark); }
.nav a { color: var(--ink-soft); text-decoration: none; margin-left: 20px; font-weight: 600; }
.nav a:hover { color: var(--clay-dark); }

main { max-width: 760px; margin: 0 auto; padding: 0 20px 60px; }

.hero { text-align: center; padding: 18px 0 26px; }
.hero h1 { font-size: 2.4rem; margin: 0 0 10px; color: var(--ink); }
.hero .sub { font-size: 1.08rem; color: var(--ink-soft); max-width: 540px; margin: 0 auto; }

/* Đồng hồ */
.timer-card {
  background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 30px 26px 26px; text-align: center; margin-bottom: 26px;
}
.mode-tabs { display: inline-flex; gap: 6px; background: var(--bg-soft); padding: 6px; border-radius: 999px; margin-bottom: 18px; }
.mode {
  border: none; background: transparent; color: var(--ink-soft);
  padding: 8px 16px; border-radius: 999px; font-weight: 600; cursor: pointer; font-family: inherit; font-size: 0.95rem;
}
.mode.active { background: var(--clay); color: #fff; box-shadow: 0 4px 12px rgba(217,140,106,0.35); }

.clock { font-size: 5.2rem; font-weight: 700; letter-spacing: 1px; line-height: 1.1; color: var(--ink); }
.clock-task { color: var(--ink-soft); margin: 6px 0 22px; min-height: 1.5em; }

.controls { display: flex; gap: 12px; justify-content: center; }
.btn {
  font-family: inherit; font-weight: 700; font-size: 1.05rem;
  border: none; border-radius: 14px; padding: 13px 30px; cursor: pointer; transition: transform .06s ease, box-shadow .2s ease;
}
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--clay); color: #fff; box-shadow: 0 6px 16px rgba(217,140,106,0.4); }
.btn-primary:hover { background: var(--clay-dark); }
.btn-ghost { background: var(--bg-soft); color: var(--ink-soft); }
.btn-ghost:hover { color: var(--ink); }

.presets { display: flex; align-items: center; gap: 8px; justify-content: center; margin: 22px 0 6px; color: var(--ink-soft); }
.preset { border: 1.5px solid #ead9c8; background: transparent; color: var(--ink-soft); border-radius: 999px; padding: 5px 14px; font-weight: 600; cursor: pointer; font-family: inherit; }
.preset.active { border-color: var(--sage); color: #5f7a5e; background: #f0f5ed; }

.counter { color: var(--ink-soft); font-size: 0.95rem; margin-top: 14px; }

/* AI */
.ai-card {
  background: linear-gradient(180deg, #fff8f0, #fff);
  border: 1.5px solid #f1e2d3; border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 28px 26px; margin-bottom: 30px;
}
.ai-card h2 { margin: 0 0 8px; }
.ai-desc { color: var(--ink-soft); margin-top: 0; }
.ai-label { display: block; font-weight: 700; margin: 14px 0 8px; }
#taskInput {
  width: 100%; resize: vertical; font-family: inherit; font-size: 1rem;
  border: 1.5px solid #ecdccb; border-radius: 14px; padding: 12px 14px; background: #fffdfa; color: var(--ink);
}
#taskInput:focus { outline: none; border-color: var(--clay); }
#planBtn { margin-top: 12px; }

.plan-status { margin-top: 16px; color: var(--ink-soft); font-weight: 600; }
.plan-result { display: grid; gap: 12px; margin-top: 18px; }
.plan-overview { background: #f0f5ed; border-radius: 14px; padding: 12px 16px; color: #5f7a5e; font-weight: 600; }
.session {
  text-align: left; background: var(--card); border: 1.5px solid #f1e2d3; border-radius: 16px;
  padding: 14px 16px; cursor: pointer; transition: border-color .2s, box-shadow .2s;
  display: flex; gap: 14px; align-items: flex-start; width: 100%; font-family: inherit;
}
.session:hover { border-color: var(--clay); box-shadow: var(--shadow); }
.session .num { background: var(--clay); color: #fff; width: 30px; height: 30px; border-radius: 50%; display: grid; place-items: center; font-weight: 700; flex-shrink: 0; }
.session .body { flex: 1; }
.session .title { font-weight: 700; color: var(--ink); }
.session .meta { color: var(--clay-dark); font-weight: 600; font-size: 0.9rem; margin: 2px 0; }
.session .tip { color: var(--ink-soft); font-size: 0.92rem; }

/* Nội dung */
.prose { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow); padding: 26px 28px; margin-bottom: 22px; }
.prose h2 { margin-top: 0; }
.prose a { color: var(--clay-dark); }
.prose details { border-top: 1px solid #f0e6da; padding: 12px 0; }
.prose summary { font-weight: 700; cursor: pointer; }
.prose details p { color: var(--ink-soft); margin: 8px 0 0; }

.site-footer { text-align: center; color: var(--ink-soft); padding: 30px 20px 50px; font-size: 0.92rem; }

@media (max-width: 560px) {
  .hero h1 { font-size: 1.9rem; }
  .clock { font-size: 4rem; }
}