/* =============================================
   CSS Reset
   ============================================= */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  overflow-x: hidden;
}

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  background-color: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  overflow-x: hidden;
  width: 100%;
}

button {
  cursor: pointer;
  border: none;
  background: none;
  font: inherit;
}

ul {
  list-style: none;
}

/* =============================================
   CSS Custom Properties (Design Tokens)
   ============================================= */
:root {
  /* Base palette */
  --color-bg:           #f4f6f9;
  --color-surface:      #ffffff;
  --color-border:       #d1d9e0;
  --color-text:         #1a1a2e;
  --color-text-muted:   #6b7280;

  /* Brand */
  --color-primary:      #4f46e5;
  --color-primary-hover:#4338ca;
  --color-primary-text: #ffffff;

  /* Game cells */
  --color-cell-bg:            #ffffff;
  --color-cell-hover:         #e0e7ff;
  --color-cell-hover-border:  #a5b4fc;
  --color-cell-select:        #a5b4fc;
  --color-cell-select-border: #6366f1;
  --color-cell-select-text:   #1e1b4b;
  --color-focus:              #4f46e5;

  /* Found / invalid states */
  --color-found:          #6ee7b7;
  --color-found-border:   #10b981;
  --color-found-text:     #065f46;
  --color-found-bg:       #d1fae5;
  --color-invalid:        #fca5a5;
  --color-invalid-border: #f87171;
  --color-invalid-text:   #7f1d1d;

  /* Loading overlay */
  --color-overlay:        rgba(255,255,255,.85);

  /* Word list */
  --color-word-pending:   #1a1a2e;
  --color-word-found:     #059669;
  --color-progress-bg:    #e5e7eb;

  /* Dismiss button (win-modal) */
  --color-btn-dismiss-bg:    #f3f4f6;
  --color-btn-dismiss-text:  #374151;
  --color-btn-dismiss-hover: #e5e7eb;

  /* Difficulty badges */
  --color-easy:         #34d399;
  --color-medium:       #fbbf24;
  --color-hard:         #f87171;

  /* Layout */
  --header-height:      60px;
  --controls-width:     260px;
  --border-radius:      8px;
  --border-radius-lg:   16px;
  --shadow-sm:          0 1px 3px rgba(0,0,0,.08);
  --shadow-md:          0 4px 12px rgba(0,0,0,.12);

  /* Transitions */
  --transition-fast:    120ms ease;
  --transition-base:    200ms ease;
}

/* ── Dark theme vars ─────────────────────────────────────────────────────────
   Applied when system prefers dark (and user hasn't forced light),
   or when user explicitly chose dark via [data-theme="dark"].
   ─────────────────────────────────────────────────────────────────────────── */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --color-bg:                 #0f0f1a;
    --color-surface:            #1e1e30;
    --color-border:             #2e2e45;
    --color-text:               #e5e7eb;
    --color-text-muted:         #9ca3af;

    --color-cell-bg:            #1e1e30;
    --color-cell-hover:         #2d2d50;
    --color-cell-hover-border:  #6366f1;
    --color-cell-select:        #4338ca;
    --color-cell-select-border: #818cf8;
    --color-cell-select-text:   #e0e7ff;
    --color-focus:              #818cf8;

    --color-found:              #065f46;
    --color-found-text:         #6ee7b7;
    --color-found-bg:           #022c22;
    --color-invalid:            #7f1d1d;
    --color-invalid-text:       #fca5a5;

    --color-overlay:            rgba(15,15,26,.85);
    --color-progress-bg:        #2e2e45;

    --color-btn-dismiss-bg:     #2e2e45;
    --color-btn-dismiss-text:   #d1d5db;
    --color-btn-dismiss-hover:  #3a3a5c;
  }
}

:root[data-theme="dark"] {
  --color-bg:                 #0f0f1a;
  --color-surface:            #1e1e30;
  --color-border:             #2e2e45;
  --color-text:               #e5e7eb;
  --color-text-muted:         #9ca3af;

  --color-cell-bg:            #1e1e30;
  --color-cell-hover:         #2d2d50;
  --color-cell-hover-border:  #6366f1;
  --color-cell-select:        #4338ca;
  --color-cell-select-border: #818cf8;
  --color-cell-select-text:   #e0e7ff;
  --color-focus:              #818cf8;

  --color-found:              #065f46;
  --color-found-text:         #6ee7b7;
  --color-found-bg:           #022c22;
  --color-invalid:            #7f1d1d;
  --color-invalid-text:       #fca5a5;

  --color-overlay:            rgba(15,15,26,.85);
  --color-progress-bg:        #2e2e45;

  --color-btn-dismiss-bg:     #2e2e45;
  --color-btn-dismiss-text:   #d1d5db;
  --color-btn-dismiss-hover:  #3a3a5c;
}

/* =============================================
   Layout Helpers
   ============================================= */
.app-header {
  width: 100%;
  max-width: 100%;
  height: var(--header-height);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}

.header-controls {
  display: flex;
  align-items: center;
  gap: .75rem;
}

.app-header h1 {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--color-primary);
  letter-spacing: -.5px;
}

.app-main {
  display: flex;
  flex-direction: row;
  gap: 1.5rem;
  padding: 1.5rem;
  width: 100%;
  max-width: 1100px;
  flex: 1;
}

.app-sidebar {
  flex: 0 0 var(--controls-width);
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.app-board {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

/* Card surface */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  padding: 1rem 1.25rem;
  box-shadow: var(--shadow-sm);
}

/* Primary action button */
.btn-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: .5rem;
  background: var(--color-primary);
  color: var(--color-primary-text);
  padding: .65rem 1.4rem;
  border-radius: var(--border-radius);
  font-weight: 600;
  font-size: .95rem;
  transition: background var(--transition-fast);
  width: 100%;
}

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

.btn-primary:disabled {
  opacity: .5;
  cursor: not-allowed;
}

/* Primary button — loading state */
.btn-primary.loading {
  opacity: .8;
  cursor: not-allowed;
  gap: .6rem;
}

.btn-primary .btn-spinner {
  display: none;
  width: 14px;
  height: 14px;
  border: 2px solid rgba(255,255,255,.4);
  border-top-color: #fff;
  border-radius: 50%;
  animation: spin .6s linear infinite;
  flex-shrink: 0;
}

.btn-primary.loading .btn-spinner {
  display: block;
}

/* Global spinner (unused directly but available) */
.spinner {
  width: 36px;
  height: 36px;
  border: 3px solid var(--color-border);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin .7s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* =============================================
   Toast notifications
   ============================================= */
#toast-container {
  position: fixed;
  bottom: 1.5rem;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: .5rem;
  z-index: 200;
  pointer-events: none;
}

.toast {
  background: var(--color-text);
  color: var(--color-surface);
  padding: .5rem 1.1rem;
  border-radius: 999px;
  font-size: .85rem;
  font-weight: 600;
  letter-spacing: .02em;
  box-shadow: var(--shadow-md);
  animation: toast-in 180ms ease, toast-out 300ms ease 1.4s forwards;
  pointer-events: none;
}

.toast.toast-found {
  background: #059669;
  color: #fff;
}

@keyframes toast-in {
  from { opacity: 0; transform: translateY(8px) scale(.95); }
  to   { opacity: 1; transform: translateY(0)  scale(1);    }
}

@keyframes toast-out {
  from { opacity: 1; }
  to   { opacity: 0; transform: translateY(-4px); }
}

/* =============================================
   Custom words input
   ============================================= */
.custom-words-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: .5rem;
}

.custom-words-label {
  font-size: .8rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: .05em;
}

.custom-words-clear {
  font-size: .78rem;
  font-weight: 500;
  color: var(--color-text-muted);
  padding: .15rem .45rem;
  border-radius: 4px;
  transition: color var(--transition-fast), background var(--transition-fast);
}

.custom-words-clear:hover {
  color: var(--color-text);
  background: var(--color-border);
}

.custom-words-input {
  width: 100%;
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  padding: .5rem .75rem;
  font: inherit;
  font-size: .9rem;
  color: var(--color-text);
  background: var(--color-bg);
  resize: vertical;
  outline: none;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.custom-words-input:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, .15);
}

.custom-words-hint {
  margin-top: .4rem;
  font-size: .75rem;
  color: var(--color-text-muted);
  line-height: 1.4;
}

/* =============================================
   Responsive
   ============================================= */
@media (max-width: 680px) {
  .app-main {
    flex-direction: column;
    padding: 1rem;
    width: 100%;
  }

  .app-sidebar {
    flex: none;
    width: 100%;
  }
}

@media (max-width: 480px) {
  .app-header {
    padding: 0 .75rem;
  }

  .header-controls {
    gap: .4rem;
  }
}