:root {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: #334155;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --accent-color: #38bdf8;
  --accent-hover: #0284c7;
  --border-color: #475569;
}

/* KELAS LIGHT THEME */
body.light-theme {
  --bg-primary: #f1f5f9;
  --bg-secondary: #ffffff;
  --bg-card: #e2e8f0;
  --text-primary: #0f172a;
  --text-secondary: #64748b;
  --accent-color: #0284c7;
  --accent-hover: #0369a1;
  --border-color: #cbd5e1;
}

body {
  margin: 0;
  font-family: 'Plus Jakarta Sans', sans-serif, system-ui;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  transition: background 0.3s ease, color 0.3s ease;
}

.app-container {
  display: flex;
  min-height: 100vh;
}

/* SIDEBAR STYLES (Responsif untuk mobile) */
.sidebar {
  width: 240px;
  background-color: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  padding: 20px;
  display: flex;
  flex-direction: column;
  transition: background 0.3s ease;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 30px;
}

.brand .logo-icon { font-size: 2rem; }
.brand h2 { margin: 0; font-size: 1.2rem; color: var(--accent-color); }
.brand small { color: var(--text-secondary); }

.nav-menu {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  color: var(--text-secondary);
  text-decoration: none;
  border-radius: 10px;
  font-weight: 500;
  transition: all 0.2s ease;
  user-select: none;
}

.nav-link:hover, .nav-link.active {
  background-color: var(--accent-color);
  color: #fff;
  font-weight: 700;
}
body.light-theme .nav-link:hover, body.light-theme .nav-link.active {
  color: #0f172a;
}

/* MAIN CONTENT */
.main-content {
  flex: 1;
  padding: 25px;
  overflow-y: auto;
}

.top-bar {
  margin-bottom: 25px;
}

.page-view {
  display: none;
}

.page-view.active {
  display: block;
  animation: fadeIn 0.3s ease-in-out;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

/* CARDS & INPUTS */
.card-calc, .welcome-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 24px;
  margin-bottom: 20px;
  transition: transform 0.3s ease, box-shadow 0.3s ease, background 0.3s ease;
}

.card-calc:hover {
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
}

.input-row {
  display: flex;
  gap: 10px;
  margin-top: 10px;
}

.input-row input, .input-row select {
  flex: 1;
  padding: 12px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: 0.9rem;
}

.btn-primary {
  background: var(--accent-color);
  color: #fff;
  border: none;
  padding: 12px 20px;
  border-radius: 8px;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.2s;
  user-select: none;
}
body.light-theme .btn-primary { color: #0f172a; }
.btn-primary:hover {
  background: var(--accent-hover);
}

/* BUTANG RESET KHAS */
.btn-reset {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
  padding: 10px 15px;
  border-radius: 8px;
  font-weight: bold;
  cursor: pointer;
  transition: all 0.2s;
}
.btn-reset:hover {
  background: rgba(244, 63, 94, 0.1);
  color: #f43f5e;
  border-color: #f43f5e;
}

.result-box {
  margin-top: 20px;
  padding: 15px;
  border-radius: 8px;
  background: rgba(56, 189, 248, 0.08);
  border: 1px solid var(--accent-color);
  display: none;
  animation: slideDown 0.4s ease-out;
}

@keyframes slideDown {
  from { opacity: 0; transform: translateY(-10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* MODAL POPUP */
.modal {
  display: none;
  position: fixed;
  z-index: 1000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(4px);
}

.modal-content {
  background-color: var(--bg-secondary);
  margin: 10% auto;
  padding: 24px;
  border: 1px solid var(--accent-color);
  border-radius: 16px;
  width: 90%;
  max-width: 500px;
  position: relative;
  color: var(--text-primary);
}

.close-modal {
  position: absolute;
  right: 16px;
  top: 12px;
  font-size: 28px;
  font-weight: bold;
  color: var(--text-secondary);
  cursor: pointer;
}

/* GRID JADUAL BERKALA */
.periodic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(75px, 1fr));
  gap: 8px;
  margin-top: 20px;
  max-height: 450px;
  overflow-y: auto;
}

.el-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 8px 4px;
  text-align: center;
  cursor: pointer;
  position: relative;
  transition: all 0.3s ease;
}

.el-card:hover {
  transform: translateY(-4px) scale(1.02);
  z-index: 10;
  border-color: var(--accent-color);
  background: var(--bg-card);
}

.el-num { font-size: 0.65rem; color: var(--text-secondary); position: absolute; top: 3px; left: 4px; }
.el-sym { font-size: 1.2rem; font-weight: 700; color: var(--accent-color); margin: 4px 0; }
.el-name { font-size: 0.65rem; color: var(--text-primary); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }

/* WARNA KUMPULAN UNSUR */
.cat-alkali { border-left: 4px solid #f43f5e !important; }
.cat-alkalibumi { border-left: 4px solid #f97316 !important; }
.cat-peralihan { border-left: 4px solid #eab308 !important; }
.cat-halogen { border-left: 4px solid #10b981 !important; }
.cat-nadir { border-left: 4px solid #8b5cf6 !important; }
.cat-metaloid { border-left: 4px solid #06b6d4 !important; }
.cat-bukanlogam { border-left: 4px solid #3b82f6 !important; }
.cat-logam { border-left: 4px solid #94a3b8 !important; }

/* TABLE RESULT */
.result-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 15px;
}

.result-table th, .result-table td {
  border: 1px solid var(--border-color);
  padding: 8px 12px;
  text-align: left;
  font-size: 0.85rem;
  color: var(--text-primary);
}

.result-table th {
  background-color: var(--bg-card);
  color: var(--accent-color);
}

/* BUTANG SALIN */
.btn-copy {
  background: var(--bg-secondary);
  color: var(--accent-color);
  border: 1px dashed var(--accent-color);
  padding: 8px 12px;
  border-radius: 6px;
  font-size: 0.85rem;
  font-weight: bold;
  cursor: pointer;
  margin-top: 15px;
  transition: all 0.2s ease;
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.btn-copy:hover {
  background: var(--accent-color);
  color: #fff;
}

/* FLASHCARD 3D */
.flashcard-element {
  background-color: transparent;
  width: 100%;
  max-width: 400px;
  height: 220px;
  margin: 0 auto;
  perspective: 1000px;
  cursor: pointer;
}

.flashcard-inner {
  position: relative;
  width: 100%;
  height: 100%;
  text-align: center;
  transition: transform 0.6s;
  transform-style: preserve-3d;
  border-radius: 16px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.15);
}

.flashcard-element.flipped .flashcard-inner {
  transform: rotateY(180deg);
}

.flashcard-front, .flashcard-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  border-radius: 16px;
  border: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: 20px;
  box-sizing: border-box;
}

.flashcard-front {
  background: var(--bg-secondary);
  color: var(--text-primary);
}

.flashcard-back {
  background: var(--bg-card);
  color: var(--text-primary);
  transform: rotateY(180deg);
}

/* MEDIA QUERY UNTUK TELEFON PINTAR (RESPONSIVE) */
@media (max-width: 768px) {
  .app-container {
    flex-direction: column;
  }
  .sidebar {
    width: 100%;
    box-sizing: border-box;
    border-right: none;
    border-bottom: 1px solid var(--border-color);
    padding: 15px;
  }
  .nav-menu {
    flex-direction: row;
    overflow-x: auto;
    padding-bottom: 5px;
  }
  .nav-link {
    white-space: nowrap;
    padding: 8px 12px;
    font-size: 0.85rem;
  }
  .brand {
    margin-bottom: 15px;
  }
  .main-content {
    padding: 15px;
  }
}