/* ==========================================================================
   Design System & Config
   ========================================================================== */
:root {
  /* Colors */
  --bg-app: #f4f6f9;
  --bg-sidebar: #ffffff;
  --bg-card: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-light: #e0e7ff;
  
  --accent: #06b6d4;
  --accent-light: #ecfeff;

  --success: #10b981;
  --success-light: #d1fae5;
  --danger: #f43f5e;
  --danger-light: #ffe4e6;

  --border: #e2e8f0;
  
  /* Fonts */
  --font-sans: 'Outfit', 'Noto Sans JP', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;

  /* Layout */
  --radius-sm: 8px;
  --radius-md: 16px;
  --radius-lg: 24px;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 25px -5px rgba(0, 0, 0, 0.05), 0 8px 10px -6px rgba(0, 0, 0, 0.05);
  --shadow-premium: 0 20px 40px -15px rgba(15, 23, 42, 0.08);

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ==========================================================================
   Reset & Base Styles
   ========================================================================== */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background-color: var(--bg-app);
  color: var(--text-primary);
  font-family: var(--font-sans);
  min-height: 100vh;
  display: flex;
  overflow: hidden; /* メインコンテンツ側でスクロールさせるため */
  -webkit-font-smoothing: antialiased;
}

/* ==========================================================================
   App Layout
   ========================================================================== */
.dashboard-container {
  display: flex;
  width: 100vw;
  height: 100vh;
}

/* Sidebar */
.sidebar {
  width: 260px;
  background-color: var(--bg-sidebar);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  padding: 32px 24px;
  flex-shrink: 0;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 40px;
}

.brand-logo {
  font-size: 1.8rem;
  animation: pulse 2s infinite;
}

.brand-name {
  font-size: 1.4rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.sidebar-nav {
  display: flex;
  flex-direction: column;
  gap: 8px;
  flex-grow: 1;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.nav-item:hover {
  background-color: var(--bg-app);
  color: var(--primary);
  transform: translateX(4px);
}

.nav-item.active {
  background-color: var(--primary-light);
  color: var(--primary);
  font-weight: 600;
}

.nav-icon {
  font-size: 1.2rem;
}

.sidebar-footer {
  border-top: 1px solid var(--border);
  padding-top: 20px;
}

.theme-info {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
}

/* Main Content Area */
.main-content {
  flex-grow: 1;
  padding: 40px 48px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 32px;
}

/* Header */
.content-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  animation: fadeInDown 0.5s ease-out;
}

.header-title h1 {
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 4px;
}

.header-title .subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.stats-overview {
  display: flex;
  gap: 16px;
}

.stat-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 12px 24px;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  align-items: center;
}

.stat-value {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--primary);
}

.stat-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-weight: 600;
  text-transform: uppercase;
}

/* Cards & Containers */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 32px;
  box-shadow: var(--shadow-premium);
  animation: fadeInUp 0.5s ease-out;
}

.card-header {
  margin-bottom: 24px;
}

.card-header h2 {
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 4px;
}

.card-header p {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* ==========================================================================
   Tab Content Control
   ========================================================================== */
.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

/* ==========================================================================
   Todo List UI
   ========================================================================== */
.todo-input-group {
  display: flex;
  gap: 12px;
  margin-bottom: 24px;
}

#todo-input {
  flex-grow: 1;
  padding: 14px 20px;
  border-radius: var(--radius-sm);
  border: 2px solid var(--border);
  font-family: inherit;
  font-size: 0.95rem;
  transition: all var(--transition-fast);
  background-color: var(--bg-app);
}

#todo-input:focus {
  outline: none;
  border-color: var(--primary);
  background-color: #ffffff;
  box-shadow: 0 0 0 4px var(--primary-light);
}

.btn {
  padding: 12px 28px;
  border-radius: var(--radius-sm);
  border: none;
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-primary {
  background-color: var(--primary);
  color: #ffffff;
}

.btn-primary:hover {
  background-color: var(--primary-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(79, 70, 229, 0.2);
}

.todo-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.todo-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  background-color: var(--bg-app);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  transition: all var(--transition-normal);
  animation: slideIn 0.3s ease-out;
}

.todo-item:hover {
  border-color: var(--text-muted);
  background-color: #ffffff;
  box-shadow: var(--shadow-md);
}

.todo-item.completed {
  opacity: 0.6;
}

.todo-item-content {
  display: flex;
  align-items: center;
  gap: 12px;
  cursor: pointer;
  flex-grow: 1;
}

.todo-checkbox {
  width: 20px;
  height: 20px;
  border-radius: 6px;
  border: 2px solid var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.todo-item.completed .todo-checkbox {
  border-color: var(--success);
  background-color: var(--success);
}

.todo-checkbox::after {
  content: '✓';
  color: #ffffff;
  font-size: 0.8rem;
  font-weight: bold;
  display: none;
}

.todo-item.completed .todo-checkbox::after {
  display: block;
}

.todo-text {
  font-size: 0.95rem;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.todo-item.completed .todo-text {
  text-decoration: line-through;
  color: var(--text-muted);
}

.btn-delete {
  background: transparent;
  border: none;
  cursor: pointer;
  padding: 8px;
  border-radius: 50%;
  font-size: 1rem;
  transition: all var(--transition-fast);
  color: var(--text-muted);
}

.btn-delete:hover {
  background-color: var(--danger-light);
  color: var(--danger);
}

/* ==========================================================================
   Idea Notebook UI
   ========================================================================== */
#idea-textarea {
  width: 100%;
  height: 320px;
  padding: 20px;
  border-radius: var(--radius-sm);
  border: 2px solid var(--border);
  background-color: var(--bg-app);
  font-family: inherit;
  font-size: 1rem;
  line-height: 1.6;
  resize: none;
  transition: all var(--transition-fast);
}

#idea-textarea:focus {
  outline: none;
  border-color: var(--accent);
  background-color: #ffffff;
  box-shadow: 0 0 0 4px var(--accent-light);
}

.save-indicator {
  margin-top: 12px;
  font-size: 0.8rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 6px;
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.save-indicator.show {
  opacity: 1;
}

/* ==========================================================================
   About Page UI
   ========================================================================== */
.about-card p {
  color: var(--text-secondary);
  font-size: 1rem;
  line-height: 1.7;
  margin-bottom: 32px;
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 24px;
}

.feature-item {
  background-color: var(--bg-app);
  border-radius: var(--radius-md);
  padding: 24px;
  border: 1px solid var(--border);
}

.feature-icon {
  font-size: 2rem;
  display: block;
  margin-bottom: 16px;
}

.feature-item h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.feature-item p {
  font-size: 0.85rem;
  line-height: 1.5;
  color: var(--text-secondary);
  margin-bottom: 0;
}

/* ==========================================================================
   Animations
   ========================================================================== */
@keyframes pulse {
  0% { transform: scale(1); }
  50% { transform: scale(1.08); }
  100% { transform: scale(1); }
}

@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(16px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ==========================================================================
   Responsive Design
   ========================================================================== */
@media (max-width: 900px) {
  body {
    overflow: auto;
  }
  .dashboard-container {
    flex-direction: column;
    height: auto;
  }
  .sidebar {
    width: 100%;
    border-right: none;
    border-bottom: 1px solid var(--border);
    padding: 20px;
  }
  .brand {
    margin-bottom: 16px;
  }
  .sidebar-nav {
    flex-direction: row;
    overflow-x: auto;
    gap: 8px;
  }
  .sidebar-footer {
    display: none;
  }
  .main-content {
    padding: 24px;
    height: auto;
    overflow-y: visible;
  }
  .content-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 16px;
  }
}