:root {
  --bg:       #0f172a;
  --surface:  #1e293b;
  --border:   #334155;
  --green:    #10b981;
  --teal:     #06b6d4;
  --text:     #f1f5f9;
  --muted:    #94a3b8;
  --red:      #ef4444;
  --yellow:   #f59e0b;
  --radius:   12px;
  --shadow:   0 4px 24px rgba(0,0,0,0.4);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Segoe UI', system-ui, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  min-height: 100vh;
}

a { color: var(--green); text-decoration: none; }
a:hover { color: var(--teal); }

/* NAV */
nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-logo {
  font-size: 1.4rem;
  font-weight: 800;
  background: linear-gradient(90deg, var(--green), var(--teal));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav-links {
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
}

.nav-links a {
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.2s;
}

.nav-links a:hover { color: var(--text); }

/* HERO */
.hero {
  text-align: center;
  padding: 60px 24px 40px;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 16px;
}

.hero h1 span {
  background: linear-gradient(90deg, var(--green), var(--teal));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  color: var(--muted);
  font-size: 1.1rem;
  max-width: 560px;
  margin: 0 auto 32px;
}

/* TOOL GRID */
.section-label {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
  padding: 0 24px 12px;
  max-width: 1100px;
  margin: 32px auto 0;
}

.tool-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
  padding: 0 24px 24px;
  max-width: 1100px;
  margin: 0 auto;
}

.tool-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  transition: border-color 0.2s, transform 0.2s;
  color: var(--text);
}

.tool-card:hover {
  border-color: var(--green);
  transform: translateY(-2px);
}

.tool-card .icon { font-size: 2rem; }
.tool-card h3 { font-size: 1rem; font-weight: 700; }
.tool-card p  { font-size: 0.88rem; color: var(--muted); flex: 1; }

.tag {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 99px;
  margin-top: 4px;
}

.tag-time    { background: rgba(16,185,129,0.15); color: var(--green); }
.tag-math    { background: rgba(245,158,11,0.15); color: var(--yellow); }
.tag-utility { background: rgba(6,182,212,0.15);  color: var(--teal); }

/* TOOL PAGE */
.tool-page {
  max-width: 680px;
  margin: 40px auto;
  padding: 0 24px 80px;
}

.tool-page h1 {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 8px;
}

.tool-page .subtitle {
  color: var(--muted);
  margin-bottom: 32px;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  margin-bottom: 20px;
  box-shadow: var(--shadow);
}

/* FORM ELEMENTS */
label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--muted);
  margin-bottom: 6px;
  margin-top: 16px;
}

label:first-child { margin-top: 0; }

input[type=text],
input[type=number],
input[type=email],
input[type=date],
select,
textarea {
  width: 100%;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  padding: 12px 14px;
  font-size: 1rem;
  outline: none;
  transition: border-color 0.2s;
}

input:focus, select:focus, textarea:focus {
  border-color: var(--green);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  background: linear-gradient(135deg, var(--green), var(--teal));
  color: #fff;
  font-weight: 700;
  font-size: 1rem;
  padding: 14px 28px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  margin-top: 20px;
  width: 100%;
  transition: opacity 0.2s, transform 0.1s;
}

.btn:hover   { opacity: 0.9; }
.btn:active  { transform: scale(0.98); }

.btn-outline {
  background: transparent;
  border: 1px solid var(--green);
  color: var(--green);
}

.result-box {
  background: rgba(16,185,129,0.08);
  border: 1px solid rgba(16,185,129,0.3);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin-top: 20px;
  display: none;
}

.result-box.show { display: block; }

.result-big {
  font-size: 2.4rem;
  font-weight: 800;
  color: var(--green);
  line-height: 1.2;
}

.result-label {
  font-size: 0.85rem;
  color: var(--muted);
  margin-top: 4px;
}

/* TIMER */
.timer-display {
  font-size: clamp(3rem, 10vw, 6rem);
  font-weight: 800;
  font-variant-numeric: tabular-nums;
  text-align: center;
  color: var(--green);
  letter-spacing: 0.05em;
  padding: 20px 0;
}

.timer-buttons {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.timer-buttons .btn {
  flex: 1;
  min-width: 80px;
}

.btn-danger { background: var(--red); }
.btn-warn   { background: var(--yellow); color: #000; }

.preset-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}

.preset-btn {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--muted);
  padding: 8px 16px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.9rem;
  transition: all 0.2s;
}

.preset-btn:hover {
  border-color: var(--green);
  color: var(--green);
}

/* COMPETITION POPUP */
.popup-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.7);
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s;
}

.popup-overlay.show {
  opacity: 1;
  pointer-events: all;
}

.popup-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 32px;
  max-width: 440px;
  width: 100%;
  position: relative;
  transform: translateY(20px);
  transition: transform 0.3s;
}

.popup-overlay.show .popup-box {
  transform: translateY(0);
}

.popup-close {
  position: absolute;
  top: 16px;
  right: 20px;
  background: none;
  border: none;
  color: var(--muted);
  font-size: 1.4rem;
  cursor: pointer;
}

.popup-prize {
  font-size: 2.5rem;
  text-align: center;
  margin-bottom: 8px;
}

.popup-box h2 {
  text-align: center;
  font-size: 1.4rem;
  margin-bottom: 8px;
}

.popup-box p {
  text-align: center;
  color: var(--muted);
  font-size: 0.9rem;
  margin-bottom: 20px;
}

.popup-tickets {
  text-align: center;
  font-size: 0.85rem;
  color: var(--teal);
  margin-top: 12px;
}

.popup-cooldown {
  text-align: center;
  font-size: 0.85rem;
  color: var(--yellow);
  margin-top: 8px;
  display: none;
}

/* DAILY PUZZLE */
.puzzle-options {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 20px;
}

.option-btn {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 14px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.95rem;
  text-align: left;
  transition: all 0.2s;
}

.option-btn:hover  { border-color: var(--green); color: var(--green); }
.option-btn.correct { border-color: var(--green); background: rgba(16,185,129,0.15); color: var(--green); }
.option-btn.wrong   { border-color: var(--red);   background: rgba(239,68,68,0.1);   color: var(--red); }

.streak-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: rgba(245,158,11,0.15);
  color: var(--yellow);
  font-weight: 700;
  padding: 6px 14px;
  border-radius: 99px;
  font-size: 0.9rem;
}

/* STATS ROW */
.stats-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 12px;
  margin-top: 20px;
}

.stat-box {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  text-align: center;
}

.stat-box .stat-num  { font-size: 1.8rem; font-weight: 800; color: var(--green); }
.stat-box .stat-lbl  { font-size: 0.78rem; color: var(--muted); margin-top: 4px; }

/* UNIT CONVERTER TABS */
.tabs {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 20px;
}

.tab-btn {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--muted);
  padding: 8px 16px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.85rem;
  transition: all 0.2s;
}

.tab-btn.active {
  border-color: var(--green);
  color: var(--green);
  background: rgba(16,185,129,0.08);
}

/* FOOTER */
footer {
  text-align: center;
  padding: 40px 24px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.85rem;
  margin-top: 40px;
}

footer a { color: var(--muted); }
footer a:hover { color: var(--green); }

/* RESPONSIVE */
@media (max-width: 600px) {
  .nav-links { display: none; }
  .tool-grid { grid-template-columns: 1fr; }
  .puzzle-options { grid-template-columns: 1fr; }
  .timer-display { font-size: 4rem; }
}

/* ─── AD SLOTS ────────────────────────────────────────────────────────────── */
.ad-slot{margin:24px auto;max-width:900px;padding:0 20px;text-align:center;}
.ad-slot .ad-label{font-size:.62rem;color:var(--muted);text-transform:uppercase;letter-spacing:1px;margin-bottom:6px;}
.temp-ad{display:flex;align-items:center;justify-content:space-between;gap:16px;padding:14px 20px;border-radius:12px;text-decoration:none;transition:filter .2s;flex-wrap:wrap;}
.temp-ad:hover{filter:brightness(1.12);}
.temp-ad .ad-left{display:flex;align-items:center;gap:14px;text-align:left;}
.temp-ad .ad-icon{font-size:1.8rem;flex-shrink:0;}
.temp-ad .ad-title{font-size:.88rem;font-weight:700;color:var(--text);margin-bottom:3px;}
.temp-ad .ad-desc{font-size:.74rem;color:var(--muted);line-height:1.45;}
.temp-ad .ad-cta{padding:9px 20px;border-radius:8px;font-size:.8rem;font-weight:700;white-space:nowrap;flex-shrink:0;}
@media(max-width:600px){
  .ad-slot{padding:0 12px;}
  .temp-ad{padding:12px 14px;gap:10px;}
  .temp-ad .ad-title{font-size:.82rem;}
  .temp-ad .ad-desc{font-size:.7rem;}
  .temp-ad .ad-cta{width:100%;text-align:center;padding:8px;}
}