/* ========================================
   CSS 변수 (Design System)
   ======================================== */
:root {
    /* Colors */
    --primary: #3C8D99;
    --secondary: #6FCCB4;
    --accent: #FFB347;
    --danger: #EF4444;
    --success: #10B981;
    --warning: #F59E0B;
    --info: #3B82F6;
    
    /* Grays */
    --gray-50: #F9FAFB;
    --gray-100: #F3F4F6;
    --gray-200: #E5E7EB;
    --gray-300: #D1D5DB;
    --gray-400: #9CA3AF;
    --gray-500: #6B7280;
    --gray-600: #4B5563;
    --gray-700: #374151;
    --gray-800: #1F2937;
    --gray-900: #111827;
    
    /* Layout */
    --background: #F8FAFC;
    --surface: #FFFFFF;
    --border: #E5E7EB;
    
    /* Text */
    --text-primary: #1a1a1a;
    --text-secondary: #6b7280;
    --text-light: #F9FAFB;
    
    /* Backgrounds */
    --bg-primary: #ffffff;
    --bg-secondary: #f3f4f6;
    --bg-hover: #f3f4f6;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 0.75rem;
    --spacing-lg: 1rem;
    --spacing-xl: 1.5rem;
    --spacing-2xl: 2rem;
    
    /* Border Radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    
    /* Font Sizes */
    --text-xs: 12px;
    --text-sm: 14px;
    --text-base: 16px;
    --text-lg: 18px;
    --text-xl: 20px;
    --text-2xl: 24px;
    --text-3xl: 30px;
    
    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

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

html {
    font-size: 16px;
}

body {
    font-family: 'Pretendard Variable', 'Noto Sans KR', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

/* ========================================
   Login Page Container
   ======================================== */
.login-page {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px 20px;
    position: relative;
}

/* ========================================
   Background Effects
   ======================================== */
.bg-gradient {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(ellipse at 20% 20%, rgba(60, 141, 153, 0.08) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 80%, rgba(111, 204, 180, 0.06) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 50%, rgba(255, 179, 71, 0.04) 0%, transparent 70%);
    pointer-events: none;
    z-index: 0;
}

.bg-grid {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-image: 
        linear-gradient(rgba(60, 141, 153, 0.03) 1px, transparent 1px),
        linear-gradient(90deg, rgba(60, 141, 153, 0.03) 1px, transparent 1px);
    background-size: 60px 60px;
    mask-image: radial-gradient(ellipse at center, black 0%, transparent 70%);
    -webkit-mask-image: radial-gradient(ellipse at center, black 0%, transparent 70%);
    pointer-events: none;
    z-index: 0;
}

/* ========================================
   Main Container
   ======================================== */
.login-container {
    width: 100%;
    max-width: 440px;
    display: flex;
    flex-direction: column;
    align-items: center;
    position: relative;
    z-index: 1;
}

/* ========================================
   Logo Section
   ======================================== */
.logo-section {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.logo {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    margin-bottom: 12px;
}

.logo-icon {
    width: 48px;
    height: 48px;
    background: linear-gradient(135deg, var(--primary) 0%, #2d6b73 100%);
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 8px 24px rgba(60, 141, 153, 0.25);
}

.logo-icon svg {
    width: 28px;
    height: 28px;
    color: var(--text-light);
}

.logo-text {
    font-size: var(--text-2xl);
    font-weight: 800;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.logo-text .accent {
    color: var(--primary);
}

.tagline {
    font-size: 15px;
    color: var(--text-secondary);
    font-weight: 400;
}

/* ========================================
   Auth Card
   ======================================== */
.auth-card {
    width: 100%;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-2xl);
    padding: 40px 32px;
    box-shadow: var(--shadow-xl);
}

.card-title {
    font-size: var(--text-2xl);
    font-weight: 700;
    color: var(--text-primary);
    text-align: center;
    margin-bottom: var(--spacing-2xl);
    letter-spacing: -0.02em;
}

/* ========================================
   Auth Tabs
   ======================================== */
.auth-tabs {
    display: flex;
    position: relative;
    margin-bottom: var(--spacing-2xl);
    background: var(--gray-100);
    border-radius: var(--radius-lg);
    padding: 4px;
}

.auth-tab {
    flex: 1;
    padding: 14px 20px;
    background: transparent;
    border: none;
    font-size: 15px;
    font-weight: 600;
    color: var(--text-secondary);
    cursor: pointer;
    position: relative;
    z-index: 1;
    transition: color var(--transition-normal);
    border-radius: 10px;
}

.auth-tab.active {
    color: var(--text-light);
}

.tab-indicator {
    position: absolute;
    top: 4px;
    bottom: 4px;
    left: 4px;
    width: calc(50% - 4px);
    background: linear-gradient(135deg, var(--primary) 0%, #2d6b73 100%);
    border-radius: 10px;
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    z-index: 0;
}

/* ========================================
   Tab Content
   ======================================== */
.tab-content {
    position: relative;
    min-height: 200px;
}

.tab-pane {
    position: absolute;
    width: 100%;
    opacity: 0;
    transform: translateX(20px);
    transition: all var(--transition-normal);
    pointer-events: none;
    visibility: hidden;
}

.tab-pane.active {
    opacity: 1;
    transform: translateX(0);
    position: relative;
    pointer-events: all;
    visibility: visible;
}

/* ========================================
   Form Styles
   ======================================== */
.form-group {
    margin-bottom: var(--spacing-xl);
}

.form-group label {
    display: block;
    margin-bottom: var(--spacing-sm);
    font-size: var(--text-sm);
    font-weight: 600;
    color: var(--gray-600);
}

.form-control {
    width: 100%;
    padding: 16px 18px;
    background: var(--gray-50);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    font-size: var(--text-base);
    color: var(--text-primary);
    transition: all var(--transition-normal);
    font-family: inherit;
}

.form-control::placeholder {
    color: var(--gray-400);
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(60, 141, 153, 0.15);
    background: var(--surface);
}

/* ========================================
   Submit Button
   ======================================== */
.submit-btn {
    width: 100%;
    padding: 16px 24px;
    background: linear-gradient(135deg, var(--primary) 0%, #2d6b73 100%);
    border: none;
    border-radius: var(--radius-lg);
    font-size: var(--text-base);
    font-weight: 700;
    color: var(--text-light);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    transition: all var(--transition-normal);
    margin-top: var(--spacing-sm);
    box-shadow: 0 8px 24px rgba(60, 141, 153, 0.25);
}

.submit-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 32px rgba(60, 141, 153, 0.35);
}

.submit-btn:active {
    transform: translateY(0);
}

.submit-btn:disabled {
    background: var(--gray-300);
    cursor: not-allowed;
    box-shadow: none;
    transform: none;
}

/* ========================================
   Error Message
   ======================================== */
.error-message {
    color: var(--danger);
    font-size: var(--text-sm);
    margin-top: 12px;
    display: none;
    text-align: center;
}

.error-message.show {
    display: block;
}

/* ========================================
   Terms Text
   ======================================== */
.terms-text {
    margin-top: var(--spacing-xl);
    font-size: 13px;
    color: var(--text-secondary);
    text-align: center;
    line-height: 1.6;
}

.terms-text a {
    color: var(--primary);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-fast);
}

.terms-text a:hover {
    color: #2d6b73;
    text-decoration: underline;
}

/* ========================================
   Help Links
   ======================================== */
.help-links {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-lg);
    margin-top: var(--spacing-2xl);
    padding-top: var(--spacing-xl);
    border-top: 1px solid var(--border);
}

.help-link {
    color: var(--text-secondary);
    font-size: var(--text-sm);
    font-weight: 500;
    text-decoration: none;
    transition: color var(--transition-fast);
}

.help-link:hover {
    color: var(--primary);
}

.divider-dot {
    width: 4px;
    height: 4px;
    background: var(--gray-400);
    border-radius: var(--radius-full);
}

/* ========================================
   Explore Link
   ======================================== */
.explore-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-2xl);
    padding: 14px 24px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    color: var(--text-secondary);
    text-decoration: none;
    font-size: var(--text-sm);
    font-weight: 500;
    transition: all var(--transition-normal);
}

.explore-link:hover {
    background: var(--bg-hover);
    border-color: var(--primary);
    color: var(--primary);
    transform: translateY(-2px);
}

.explore-icon {
    font-size: var(--text-base);
}

/* ========================================
   Loading Overlay
   ======================================== */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(248, 250, 252, 0.9);
    backdrop-filter: blur(8px);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 9999;
}

.loading-overlay.active {
    display: flex;
}

.loading-spinner {
    width: 48px;
    height: 48px;
    border: 3px solid var(--gray-200);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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

/* ========================================
   RESPONSIVE STYLES
   ======================================== */

/* Tablet */
@media (max-width: 768px) {
    .login-page {
        padding: 32px 20px;
    }
    
    .auth-card {
        padding: 32px 24px;
        border-radius: var(--radius-xl);
    }
    
    .card-title {
        font-size: 22px;
        margin-bottom: 28px;
    }
    
    .logo-icon {
        width: 44px;
        height: 44px;
    }
    
    .logo-text {
        font-size: 26px;
    }
}

/* Mobile */
@media (max-width: 480px) {
    .login-page {
        padding: 24px 16px;
        align-items: flex-start;
        padding-top: 60px;
    }
    
    .logo-section {
        margin-bottom: var(--spacing-xl);
    }
    
    .logo-icon {
        width: 40px;
        height: 40px;
        border-radius: var(--radius-lg);
    }
    
    .logo-icon svg {
        width: 24px;
        height: 24px;
    }
    
    .logo-text {
        font-size: var(--text-2xl);
    }
    
    .tagline {
        font-size: var(--text-sm);
    }
    
    .auth-card {
        padding: 28px 20px;
        border-radius: var(--radius-xl);
    }
    
    .card-title {
        font-size: var(--text-xl);
        margin-bottom: var(--spacing-xl);
    }
    
    .auth-tabs {
        margin-bottom: var(--spacing-xl);
    }
    
    .auth-tab {
        padding: 12px 16px;
        font-size: var(--text-sm);
    }
    
    .form-control {
        padding: 14px 16px;
        font-size: var(--text-base); /* iOS zoom 방지 */
    }
    
    .submit-btn {
        padding: 14px 20px;
        font-size: 15px;
    }
    
    .help-links {
        gap: var(--spacing-md);
        margin-top: var(--spacing-xl);
        padding-top: var(--spacing-xl);
    }
    
    .help-link {
        font-size: 13px;
    }
    
    .explore-link {
        margin-top: var(--spacing-xl);
        padding: 12px 20px;
        font-size: 13px;
    }
    
    .terms-text {
        font-size: var(--text-xs);
    }
}

/* Small Mobile */
@media (max-width: 360px) {
    .login-page {
        padding: 20px 12px;
        padding-top: 40px;
    }
    
    .auth-card {
        padding: 24px 16px;
    }
    
    .card-title {
        font-size: var(--text-lg);
    }
    
    .form-group {
        margin-bottom: var(--spacing-lg);
    }
    
    .form-control {
        padding: 12px 14px;
    }
}

/* Safe Area (iPhone X+) */
@supports (padding-bottom: env(safe-area-inset-bottom)) {
    .login-page {
        padding-bottom: calc(24px + env(safe-area-inset-bottom));
    }
}

/* 고대비 모드 지원 */
@media (prefers-contrast: high) {
    .form-control {
        border-width: 2px;
    }
    
    .auth-card {
        border-width: 2px;
    }
}

/* 모션 감소 설정 지원 */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        transition-duration: 0.01ms !important;
    }
}