/* ============================================
   按鈕組件樣式
   ============================================ */

/* ========== 基礎按鈕樣式 ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-lg);
  border-radius: var(--btn-radius);
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  line-height: var(--leading-none);
  text-decoration: none;
  cursor: pointer;
  transition: all var(--duration-normal) var(--ease-out);
  user-select: none;
  border: 1px solid transparent;
  position: relative;
  overflow: hidden;
}

.btn:focus {
  outline: none;
}

.btn:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.btn:disabled:not(.btn-danger) {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none !important;
}

/* ========== 按鈕尺寸變體 ========== */
.btn-sm {
  padding: var(--space-xs) var(--space-md);
  font-size: var(--text-xs);
  border-radius: var(--radius-md);
}

.btn-md {
  padding: var(--space-sm) var(--space-lg);
  font-size: var(--text-sm);
  border-radius: var(--radius-lg);
}

.btn-lg {
  padding: var(--space-md) var(--space-xl);
  font-size: var(--text-base);
  border-radius: var(--radius-xl);
}

/* ========== 主要按鈕 (Primary) - Style 3: 純色 ========== */
.btn-primary {
  background: var(--btn-primary-bg);
  color: white;
  border: 1px solid var(--primary);
  box-shadow: var(--btn-shadow);
}

.btn-primary:hover {
  background: var(--btn-primary-bg-hover);
  box-shadow: var(--btn-shadow-hover);
}

.btn-primary:active {
  box-shadow: var(--shadow-xs);
}

/* ========== 輔助按鈕 (Secondary) ========== */
.btn-secondary {
  background: var(--bg-secondary);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-xs);
}

.btn-secondary:hover {
  background: var(--neutral-200);
  border-color: var(--neutral-300);
  box-shadow: var(--btn-shadow-hover);
  transform: var(--hover-lift);
}

.btn-secondary:active {
  transform: translateY(0);
  box-shadow: var(--shadow-xs);
}

/* ========== 輪廓按鈕 (Outline) ========== */
.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 2px solid var(--primary);
}

.btn-outline:hover {
  background: var(--primary);
  color: white;
  box-shadow: var(--btn-shadow-hover);
}

/* ========== 幽靈按鈕 (Ghost) ========== */
.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
  border: none;
}

.btn-ghost:hover {
  background: var(--neutral-100);
  color: var(--text-primary);
}

/* ========== 危險按鈕 (Danger) - Style 3: 純色 ========== */
.btn-danger {
  background: var(--error);
  color: white;
  border: 1px solid var(--error);
}

/* 危險按鈕啟用狀態 - 完整紅色 */
.btn-danger:not(.btn-disabled):not(:disabled) {
  background: var(--error) !important;
  color: white !important;
  opacity: 1 !important;
  cursor: pointer !important;
}

/* 危險按鈕禁用狀態 - 淺紅色 */
.btn-danger.btn-disabled,
.btn-danger:disabled {
  background: var(--error-light) !important;
  color: white !important;
  opacity: 0.6 !important;
  cursor: not-allowed !important;
  transform: none !important;
  box-shadow: none !important;
}

.btn-danger.btn-disabled:hover,
.btn-danger:disabled:hover {
  background: var(--error-light) !important;
  color: white !important;
  transform: none !important;
  box-shadow: none !important;
  opacity: 0.6 !important;
}

/* 危險按鈕啟用狀態的 hover 效果 */
.btn-danger:not(.btn-disabled):not(:disabled):hover {
  background: var(--error-dark) !important;
  box-shadow: var(--btn-shadow-hover);
  transform: var(--hover-lift);
}

/* ========== 升級按鈕 (Upgrade) - Style 3: 純色 ========== */
.btn-upgrade {
  background: var(--upgrade-bg);
  color: white;
  border: 1px solid var(--upgrade-border);
  box-shadow: var(--upgrade-shadow);
}

.btn-upgrade:hover {
  background: var(--upgrade-bg-hover);
  box-shadow: var(--upgrade-shadow-hover);
  transform: var(--hover-lift);
}

.btn-upgrade:active {
  transform: translateY(0);
  box-shadow: var(--upgrade-shadow);
}

/* ========== Google 登入按鈕 ========== */
.btn-google {
  background: white;
  color: var(--neutral-700);
  border: 2px solid var(--neutral-200);
  box-shadow: var(--shadow-sm);
  position: relative;
}

.btn-google:hover {
  border-color: var(--neutral-300);
  box-shadow: var(--btn-shadow-hover);
  transform: var(--hover-lift);
}

.btn-google::before {
  content: '';
  display: inline-block;
  width: 18px;
  height: 18px;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'%3E%3Cpath fill='%234285F4' d='M22.56 12.25c0-.78-.07-1.53-.2-2.25H12v4.26h5.92c-.26 1.37-1.04 2.53-2.21 3.31v2.77h3.57c2.08-1.92 3.28-4.74 3.28-8.09z'/%3E%3Cpath fill='%2334A853' d='M12 23c2.97 0 5.46-.98 7.28-2.66l-3.57-2.77c-.98.66-2.23 1.06-3.71 1.06-2.86 0-5.29-1.93-6.16-4.53H2.18v2.84C3.99 20.53 7.7 23 12 23z'/%3E%3Cpath fill='%23FBBC05' d='M5.84 14.09c-.22-.66-.35-1.36-.35-2.09s.13-1.43.35-2.09V7.07H2.18C1.43 8.55 1 10.22 1 12s.43 3.45 1.18 4.93l2.85-2.22.81-.62z'/%3E%3Cpath fill='%23EA4335' d='M12 5.38c1.62 0 3.06.56 4.21 1.64l3.15-3.15C17.45 2.09 14.97 1 12 1 7.7 1 3.99 3.47 2.18 7.07l3.66 2.84c.87-2.6 3.3-4.53 6.16-4.53z'/%3E%3C/svg%3E");
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center;
  margin-right: var(--space-sm);
}

/* ========== 載入狀態 ========== */
.btn-loading {
  position: relative;
  color: transparent !important;
}

.btn-loading::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 16px;
  height: 16px;
  margin: -8px 0 0 -8px;
  border: 2px solid transparent;
  border-top-color: currentColor;
  border-radius: 50%;
  animation: button-spin 1s linear infinite;
}

@keyframes button-spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

/* ========== 圓形按鈕 ========== */
.btn-circle {
  width: 40px;
  height: 40px;
  padding: 0;
  border-radius: var(--radius-full);
}

.btn-circle.btn-sm {
  width: 32px;
  height: 32px;
}

.btn-circle.btn-lg {
  width: 48px;
  height: 48px;
}

/* ========== 全寬按鈕 ========== */
.btn-full {
  width: 100%;
}

/* ========== 按鈕組 ========== */
.btn-group {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
}

.btn-group .btn:not(:first-child) {
  margin-left: -1px;
  border-radius: 0;
}

.btn-group .btn:first-child {
  border-top-right-radius: 0;
  border-bottom-right-radius: 0;
}

.btn-group .btn:last-child {
  border-top-left-radius: 0;
  border-bottom-left-radius: 0;
}

.btn-group .btn:not(:first-child):not(:last-child) {
  border-radius: 0;
}

/* ========== 懸浮效果 ========== */
.btn-hover-lift:hover {
  transform: var(--hover-lift);
  box-shadow: var(--hover-shadow);
}

.btn-hover-glow:hover {
  box-shadow: 0 0 20px var(--primary-200);
}

/* ========== 響應式設計 ========== */
@media (max-width: 768px) {
  .btn {
    padding: var(--space-md) var(--space-lg);
    font-size: var(--text-base);
  }
  
  .btn-sm {
    padding: var(--space-sm) var(--space-md);
  }
  
  .btn-lg {
    padding: var(--space-lg) var(--space-2xl);
  }
  
  .btn-group {
    flex-direction: column;
    width: 100%;
  }
  
  .btn-group .btn {
    width: 100%;
    margin-left: 0;
    margin-top: -1px;
    border-radius: var(--radius-lg);
  }
  
  .btn-group .btn:first-child {
    margin-top: 0;
    border-bottom-left-radius: 0;
    border-bottom-right-radius: 0;
  }
  
  .btn-group .btn:last-child {
    border-top-left-radius: 0;
    border-top-right-radius: 0;
  }
  
  .btn-group .btn:not(:first-child):not(:last-child) {
    border-radius: 0;
  }
}

/* ========== 高對比度支援 ========== */
@media (prefers-contrast: high) {
  .btn {
    border-width: 2px;
  }
  
  .btn-primary {
    background: var(--btn-primary-bg);
    border-color: var(--primary-dark);
  }
  
  .btn-secondary {
    border-color: var(--neutral-600);
  }
}

/* ========== 減少動畫支援 ========== */
@media (prefers-reduced-motion: reduce) {
  .btn {
    transition: none;
  }
  
  .btn:hover {
    transform: none;
  }
  
  .btn-loading::after {
    animation: none;
  }
}