/* ==========================================================================
   Đồng Hồ Pomodoro — WebEasier
   Pure CSS. No framework. Mobile-first, responsive, dark-mode aware.
   ========================================================================== */

:root {
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-primary-soft: #eff6ff;
  --color-accent-break: #16a34a;
  --color-accent-long: #7c3aed;

  --color-bg: #ffffff;
  --color-bg-soft: #f8fafc;
  --color-card: #ffffff;
  --color-border: #e2e8f0;
  --color-text-main: #0f172a;
  --color-text-body: #475569;
  --color-text-muted: #94a3b8;

  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 22px;
  --shadow-card: 0 2px 16px rgba(15, 23, 42, 0.06);
  --shadow-card-lg: 0 12px 40px rgba(15, 23, 42, 0.10);
  --ease: cubic-bezier(0.4, 0, 0.2, 1);
  --focus-ring: 0 0 0 3px rgba(37, 99, 235, 0.35);
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-primary: #60a5fa;
    --color-primary-dark: #3b82f6;
    --color-primary-soft: rgba(96, 165, 250, 0.12);
    --color-accent-break: #4ade80;
    --color-accent-long: #a78bfa;

    --color-bg: #0b1220;
    --color-bg-soft: #0f172a;
    --color-card: #131b2e;
    --color-border: #263248;
    --color-text-main: #f1f5f9;
    --color-text-body: #cbd5e1;
    --color-text-muted: #7d8aa3;
    --shadow-card: 0 2px 16px rgba(0, 0, 0, 0.35);
    --shadow-card-lg: 0 16px 48px rgba(0, 0, 0, 0.45);
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: "Segoe UI", system-ui, -apple-system, Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--color-text-main);
  background: var(--color-bg);
  line-height: 1.5;
}

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

a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.container {
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

/* Visible, sufficient-contrast focus state everywhere */
a:focus-visible,
button:focus-visible,
input:focus-visible,
summary:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
}

.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}

/* ==========================================================================
   Header
   ========================================================================== */

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
}

.navbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.85rem 0;
}

.navbar-brand {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--color-text-main);
}
.navbar-brand:hover { text-decoration: none; }
.navbar-brand img { height: 32px; width: auto; }
.brand-accent { color: var(--color-primary); }

.nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 0.4rem 0.6rem;
  cursor: pointer;
  color: var(--color-text-main);
}
.nav-toggle svg { width: 20px; height: 20px; }

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-links a {
  color: var(--color-text-body);
  font-size: 0.9rem;
  font-weight: 500;
}
.nav-links a[aria-current="page"] { color: var(--color-primary); font-weight: 700; }

.navbar-cta {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: var(--color-primary);
  color: #fff;
  font-size: 0.85rem;
  font-weight: 700;
  padding: 0.55rem 1.1rem;
  border-radius: 99px;
  white-space: nowrap;
}
.navbar-cta:hover { background: var(--color-primary-dark); text-decoration: none; }

.nav-right { display: flex; align-items: center; gap: 1.5rem; }

@media (max-width: 760px) {
  .nav-toggle { display: inline-flex; align-items: center; justify-content: center; }
  .nav-right {
    position: absolute; top: 100%; left: 0; right: 0;
    background: var(--color-bg); border-bottom: 1px solid var(--color-border);
    flex-direction: column; align-items: stretch; gap: 0;
    padding: 0.5rem 1.25rem 1rem;
    display: none;
  }
  .nav-right.is-open { display: flex; }
  .nav-links { flex-direction: column; align-items: flex-start; gap: 0; width: 100%; }
  .nav-links li { width: 100%; }
  .nav-links a { display: block; padding: 0.7rem 0; border-bottom: 1px solid var(--color-border); }
  .navbar-cta { margin-top: 0.75rem; justify-content: center; }
}

/* ==========================================================================
   Breadcrumb
   ========================================================================== */

.breadcrumb {
  display: flex; flex-wrap: wrap; align-items: center; gap: 0.35rem;
  list-style: none; margin: 0 0 1rem; padding: 0;
  font-size: 0.8rem; color: var(--color-text-muted);
}
.breadcrumb a { color: var(--color-text-body); }
.breadcrumb .sep { color: var(--color-text-muted); }

/* ==========================================================================
   Hero
   ========================================================================== */

.hero {
  padding: 2.5rem 0 1.5rem;
  background: linear-gradient(135deg, var(--color-primary-soft) 0%, var(--color-bg) 65%);
}

.eyebrow {
  display: inline-block;
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase;
  color: var(--color-primary);
  background: var(--color-primary-soft);
  border: 1px solid var(--color-primary);
  border-radius: 99px;
  padding: 0.3rem 0.75rem;
  margin-bottom: 0.9rem;
}

.hero h1 {
  font-size: clamp(1.75rem, 4.2vw, 2.6rem);
  font-weight: 800;
  line-height: 1.2;
  margin: 0 0 0.75rem;
  max-width: 720px;
  color: var(--color-text-main);
}

.hero-subtitle {
  font-size: 1rem;
  color: var(--color-text-body);
  max-width: 620px;
  margin: 0 0 1.25rem;
}

.hero-badges {
  list-style: none; margin: 0; padding: 0;
  display: flex; flex-wrap: wrap; gap: 0.5rem;
}
.hero-badges li {
  display: flex; align-items: center; gap: 0.35rem;
  font-size: 0.78rem; font-weight: 600; color: var(--color-text-body);
  background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: 99px; padding: 0.3rem 0.75rem;
}
.hero-badges .dot { color: var(--color-accent-break); font-weight: 900; }

/* ==========================================================================
   Timer section
   ========================================================================== */

.timer-section { padding: 1.5rem 0 3rem; }

.timer-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1.5rem;
  align-items: start;
}

@media (min-width: 900px) {
  .timer-layout { grid-template-columns: minmax(0, 1fr) 320px; }
}

.timer-card {
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card-lg);
  padding: 2rem 1.5rem 2.25rem;
  text-align: center;
  transition: border-color 220ms var(--ease);
}

.timer-card[data-session="focus"] { border-top: 4px solid var(--color-primary); }
.timer-card[data-session="shortBreak"] { border-top: 4px solid var(--color-accent-break); }
.timer-card[data-session="longBreak"] { border-top: 4px solid var(--color-accent-long); }

.session-heading { display: flex; flex-direction: column; align-items: center; gap: 0.2rem; margin-bottom: 1.25rem; }
.session-label {
  font-size: 1.05rem; font-weight: 800; letter-spacing: 0.01em;
  color: var(--color-text-main);
}
.timer-card[data-session="focus"] .session-label { color: var(--color-primary); }
.timer-card[data-session="shortBreak"] .session-label { color: var(--color-accent-break); }
.timer-card[data-session="longBreak"] .session-label { color: var(--color-accent-long); }

.session-status { font-size: 0.8rem; color: var(--color-text-muted); }

.timer-ring-wrap {
  position: relative;
  width: min(280px, 68vw);
  height: min(280px, 68vw);
  margin: 0 auto 1.5rem;
}

.progress-ring { width: 100%; height: 100%; transform: rotate(-90deg); }
.progress-ring-bg { fill: none; stroke: var(--color-border); stroke-width: 10; }
.progress-ring-fg {
  fill: none;
  stroke: var(--color-primary);
  stroke-width: 10;
  stroke-linecap: round;
  transition: stroke-dashoffset 240ms linear, stroke 220ms var(--ease);
}
.timer-card[data-session="shortBreak"] .progress-ring-fg { stroke: var(--color-accent-break); }
.timer-card[data-session="longBreak"] .progress-ring-fg { stroke: var(--color-accent-long); }

.time-display {
  position: absolute; inset: 0;
  display: flex; align-items: center; justify-content: center;
  font-size: clamp(2.4rem, 9vw, 3.4rem);
  font-weight: 800;
  font-variant-numeric: tabular-nums;
  color: var(--color-text-main);
  letter-spacing: 0.02em;
}

.session-dots {
  display: flex; justify-content: center; gap: 0.5rem; margin-bottom: 1.5rem;
}
.session-dot {
  width: 10px; height: 10px; border-radius: 50%;
  background: var(--color-border);
  transition: background 220ms var(--ease), transform 220ms var(--ease);
}
.session-dot.is-done { background: var(--color-primary); }
.session-dot.is-current { box-shadow: var(--focus-ring); transform: scale(1.2); }

.timer-controls {
  display: flex; align-items: center; justify-content: center; gap: 0.75rem; flex-wrap: wrap;
}

.btn {
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 700;
  border-radius: 99px;
  padding: 0.75rem 1.5rem;
  border: 1.5px solid transparent;
  cursor: pointer;
  display: inline-flex; align-items: center; gap: 0.5rem;
  transition: transform 150ms var(--ease), background 150ms var(--ease), border-color 150ms var(--ease), box-shadow 150ms var(--ease);
}
.btn:active { transform: translateY(1px); }

.btn-primary {
  background: var(--color-primary);
  color: #fff;
  box-shadow: 0 8px 24px rgba(37, 99, 235, 0.32);
  padding: 0.9rem 2.25rem;
  font-size: 1rem;
}
.btn-primary:hover { background: var(--color-primary-dark); }

.btn-secondary {
  background: var(--color-bg-soft);
  color: var(--color-text-main);
  border-color: var(--color-border);
}
.btn-secondary:hover { border-color: var(--color-primary); color: var(--color-primary); }

.btn-icon-label { display: inline-flex; align-items: center; gap: 0.4rem; }

.timer-live-region { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0,0,0,0); }

/* ---------------- Side panel (settings + notifications) ---------------- */

.side-panel {
  display: flex; flex-direction: column; gap: 1rem;
}

.panel-card {
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-card);
  padding: 1.25rem;
}

.panel-title {
  display: flex; align-items: center; justify-content: space-between;
  font-size: 0.95rem; font-weight: 700; color: var(--color-text-main);
  margin: 0 0 0.25rem;
}

.panel-toggle-btn {
  background: none; border: none; cursor: pointer;
  color: var(--color-primary); font-size: 0.85rem; font-weight: 700;
  font-family: inherit; padding: 0.25rem 0.4rem;
}

.stat-row {
  display: flex; align-items: baseline; justify-content: space-between;
  padding: 0.5rem 0; border-bottom: 1px dashed var(--color-border);
  font-size: 0.85rem; color: var(--color-text-body);
}
.stat-row:last-child { border-bottom: none; }
.stat-row strong { font-size: 1.05rem; color: var(--color-text-main); }

.settings-panel { margin-top: 0.75rem; }
.settings-panel[hidden] { display: none; }

.form-group { margin-bottom: 0.9rem; }
.form-group label {
  display: block; font-size: 0.8rem; font-weight: 600; color: var(--color-text-body);
  margin-bottom: 0.35rem;
}
.form-group .hint { font-size: 0.72rem; color: var(--color-text-muted); margin-top: 0.3rem; }

.form-control {
  width: 100%;
  font-family: inherit;
  font-size: 0.95rem;
  padding: 0.6rem 0.75rem;
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-bg);
  color: var(--color-text-main);
}
.form-control:focus { border-color: var(--color-primary); }

.settings-error {
  font-size: 0.8rem; color: #dc2626; background: rgba(220, 38, 38, 0.08);
  border: 1px solid rgba(220, 38, 38, 0.3); border-radius: var(--radius-sm);
  padding: 0.6rem 0.75rem; margin-bottom: 0.9rem;
}
.settings-error[hidden] { display: none; }

.settings-saved {
  font-size: 0.8rem; color: var(--color-accent-break); background: rgba(22, 163, 74, 0.08);
  border: 1px solid rgba(22, 163, 74, 0.3); border-radius: var(--radius-sm);
  padding: 0.5rem 0.75rem; margin-top: 0.5rem;
}
.settings-saved[hidden] { display: none; }

.btn-block { width: 100%; justify-content: center; }

.notif-status { font-size: 0.8rem; color: var(--color-text-body); margin: 0 0 0.75rem; }

/* ==========================================================================
   Instructions / How it works
   ========================================================================== */

.section { padding: 3.5rem 0; }
.section-soft { background: var(--color-bg-soft); }

.section-head { text-align: center; max-width: 640px; margin: 0 auto 2.25rem; }
.section-head h2 { font-size: clamp(1.35rem, 3vw, 1.75rem); font-weight: 800; margin: 0 0 0.5rem; color: var(--color-text-main); }
.section-head p { font-size: 0.92rem; color: var(--color-text-body); margin: 0; }

.steps-grid {
  display: grid; grid-template-columns: 1fr; gap: 1.5rem;
}
@media (min-width: 720px) { .steps-grid { grid-template-columns: repeat(3, 1fr); } }

.step-card { text-align: center; }
.step-num {
  width: 2.6rem; height: 2.6rem; margin: 0 auto 0.85rem;
  border-radius: 50%; background: var(--color-primary); color: #fff;
  display: flex; align-items: center; justify-content: center;
  font-weight: 800; font-size: 1.05rem;
}
.step-title { font-size: 1rem; font-weight: 700; margin: 0 0 0.4rem; color: var(--color-text-main); }
.step-desc { font-size: 0.87rem; color: var(--color-text-body); margin: 0; line-height: 1.7; }

/* ==========================================================================
   Features
   ========================================================================== */

.features-grid {
  display: grid; grid-template-columns: 1fr; gap: 1.1rem;
}
@media (min-width: 640px) { .features-grid { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 960px) { .features-grid { grid-template-columns: repeat(4, 1fr); } }

.feature-card {
  background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: var(--radius-md); padding: 1.35rem;
  box-shadow: var(--shadow-card);
}
.feature-title { font-size: 0.92rem; font-weight: 700; margin: 0.6rem 0 0.35rem; color: var(--color-text-main); }
.feature-desc { font-size: 0.83rem; color: var(--color-text-body); margin: 0; line-height: 1.65; }
.feature-icon {
  width: 2.4rem; height: 2.4rem; border-radius: 10px;
  background: var(--color-primary-soft); color: var(--color-primary);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.1rem;
}

/* ==========================================================================
   FAQ (native <details>/<summary> — accessible, no JS required)
   ========================================================================== */

.faq-list { max-width: 760px; margin: 0 auto; display: flex; flex-direction: column; gap: 0.75rem; }

.faq-item {
  background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: var(--radius-md); overflow: hidden;
}

.faq-item summary {
  cursor: pointer;
  list-style: none;
  padding: 1rem 1.25rem;
  font-size: 0.92rem; font-weight: 700; color: var(--color-text-main);
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after {
  content: "+";
  font-size: 1.2rem; font-weight: 400; color: var(--color-primary);
  flex-shrink: 0;
}
.faq-item[open] summary::after { content: "–"; }
.faq-item[open] summary { border-bottom: 1px solid var(--color-border); }

.faq-answer { padding: 0.9rem 1.25rem 1.15rem; font-size: 0.87rem; color: var(--color-text-body); line-height: 1.75; margin: 0; }

/* ==========================================================================
   SEO article
   ========================================================================== */

.article { max-width: 760px; margin: 0 auto; }
.article h2 { font-size: 1.2rem; font-weight: 800; margin: 2rem 0 0.75rem; color: var(--color-text-main); }
.article h2:first-child { margin-top: 0; }
.article p { font-size: 0.9rem; color: var(--color-text-body); line-height: 1.85; margin: 0 0 1rem; }
.article ul, .article ol { font-size: 0.9rem; color: var(--color-text-body); line-height: 1.85; padding-left: 1.4rem; margin: 0 0 1rem; }
.article li { margin-bottom: 0.4rem; }
.article strong { color: var(--color-text-main); }

/* ==========================================================================
   Related tools
   ========================================================================== */

.related-grid { display: grid; grid-template-columns: 1fr; gap: 1rem; }
@media (min-width: 640px) { .related-grid { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 960px) { .related-grid { grid-template-columns: repeat(4, 1fr); } }

.related-card {
  display: block; background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: var(--radius-md); padding: 1.1rem; box-shadow: var(--shadow-card);
  transition: transform 200ms var(--ease), box-shadow 200ms var(--ease);
}
.related-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-card-lg); text-decoration: none; }
.related-name { font-size: 0.88rem; font-weight: 700; color: var(--color-text-main); margin-bottom: 0.3rem; }
.related-desc { font-size: 0.78rem; color: var(--color-text-body); margin: 0; line-height: 1.6; }

/* ==========================================================================
   Footer
   ========================================================================== */

.site-footer { background: var(--color-bg-soft); border-top: 1px solid var(--color-border); padding: 3rem 0 1.5rem; }
.footer-grid { display: grid; grid-template-columns: 1fr; gap: 2rem; }
@media (min-width: 720px) { .footer-grid { grid-template-columns: 1.4fr 1fr 1fr; } }
.footer-brand-desc { font-size: 0.85rem; color: var(--color-text-body); max-width: 320px; line-height: 1.7; }
.footer-heading { font-size: 0.85rem; font-weight: 700; color: var(--color-text-main); margin: 0 0 0.75rem; text-transform: uppercase; letter-spacing: 0.04em; }
.footer-links { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 0.5rem; }
.footer-links a { font-size: 0.85rem; color: var(--color-text-body); }
.footer-bottom { border-top: 1px solid var(--color-border); margin-top: 2.5rem; padding-top: 1.25rem; font-size: 0.78rem; color: var(--color-text-muted); text-align: center; }

/* ==========================================================================
   Toast (session-complete confirmation)
   ========================================================================== */

.toast {
  position: fixed; left: 50%; bottom: 1.5rem; transform: translate(-50%, calc(100% + 1.5rem));
  background: #0f172a; color: #e2e8f0; border: 1px solid #1e293b;
  border-radius: 12px; padding: 0.75rem 1.25rem; font-size: 0.85rem; font-weight: 600;
  box-shadow: 0 12px 32px rgba(0,0,0,0.35);
  transition: transform 260ms var(--ease);
  z-index: 200;
}
.toast.is-visible { transform: translate(-50%, 0); }