/* ============================================
   CSS Variables & Design Tokens
   Professional Clean Design
   ============================================ */
:root {
    /* Colors - Clean Blue Theme */
    --color-primary: #2563eb;
    --color-primary-dark: #1d4ed8;
    --color-primary-light: #3b82f6;
    --color-accent: #0ea5e9;
    --color-accent-light: #38bdf8;

    --color-bg: #0a0a0f;
    --color-bg-secondary: #111118;
    --color-bg-tertiary: #1a1a24;
    --color-bg-card: #15151f;

    --color-text: #f1f5f9;
    --color-text-secondary: #94a3b8;
    --color-text-muted: #64748b;

    --color-border: rgba(255, 255, 255, 0.08);
    --color-border-hover: rgba(255, 255, 255, 0.15);

    --color-success: #10b981;
    --color-error: #ef4444;
    --color-warning: #f59e0b;

    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    --font-size-4xl: 2.5rem;

    /* Spacing */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-10: 2.5rem;
    --space-12: 3rem;
    --space-16: 4rem;

    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.25rem;
    --radius-full: 9999px;

    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 20px rgba(0, 0, 0, 0.4);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 30px rgba(37, 99, 235, 0.2);

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 200ms ease;
    --transition-slow: 300ms ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text);
    background: var(--color-bg);
    min-height: 100vh;
    overflow-x: hidden;
}

/* Subtle Background Pattern */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background:
        radial-gradient(ellipse at 20% 0%, rgba(37, 99, 235, 0.08) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 100%, rgba(14, 165, 233, 0.05) 0%, transparent 50%);
    pointer-events: none;
    z-index: -1;
}

/* ============================================
   Typography
   ============================================ */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.3;
    color: var(--color-text);
}

h1 { font-size: var(--font-size-4xl); }
h2 { font-size: var(--font-size-3xl); }
h3 { font-size: var(--font-size-xl); }

p {
    color: var(--color-text-secondary);
}

a {
    color: var(--color-primary-light);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--color-accent-light);
}

/* ============================================
   Header & Navigation
   ============================================ */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    padding: var(--space-4) var(--space-6);
    background: rgba(10, 10, 15, 0.85);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--color-border);
}

.nav {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--color-text);
    transition: opacity var(--transition-fast);
}

.logo:hover {
    color: var(--color-text);
    opacity: 0.9;
}

.logo-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--color-primary-light);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: var(--space-2);
}

.nav-link {
    color: var(--color-text-secondary);
    font-weight: 500;
    font-size: var(--font-size-sm);
    padding: var(--space-2) var(--space-4);
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast);
}

.nav-link:hover {
    color: var(--color-text);
    background: var(--color-bg-tertiary);
}

.nav-link.active {
    color: var(--color-text);
    background: var(--color-bg-tertiary);
}

/* Language Switcher */
.lang-switcher {
    display: flex;
    gap: var(--space-1);
    margin-left: var(--space-4);
    padding-left: var(--space-4);
    border-left: 1px solid var(--color-border);
}

.lang-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-1);
    background: transparent;
    border: 2px solid transparent;
    border-radius: var(--radius-sm);
    cursor: pointer;
    opacity: 0.5;
    transition: all var(--transition-fast);
}

.lang-btn:hover {
    opacity: 0.8;
}

.lang-btn.active {
    opacity: 1;
    border-color: var(--color-primary);
}

.lang-btn svg {
    display: block;
    border-radius: 2px;
}

/* ============================================
   Main Content
   ============================================ */
.main {
    padding-top: 80px;
    min-height: 100vh;
}

/* ============================================
   Buttons
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    padding: var(--space-3) var(--space-5);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    font-weight: 500;
    border: none;
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition-base);
}

.btn-primary {
    background: var(--color-primary);
    color: var(--color-text);
    box-shadow: var(--shadow-md), 0 0 20px rgba(37, 99, 235, 0.3);
}

.btn-primary:hover {
    background: var(--color-primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-lg), 0 0 30px rgba(37, 99, 235, 0.4);
}

.btn-secondary {
    background: var(--color-bg-tertiary);
    color: var(--color-text);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover {
    background: var(--color-bg-card);
    border-color: var(--color-border-hover);
}

.btn-large {
    padding: var(--space-4) var(--space-8);
    font-size: var(--font-size-base);
    border-radius: var(--radius-xl);
}

.btn-full {
    width: 100%;
}

/* ============================================
   Form Elements
   ============================================ */
.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.form-group label {
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--color-text);
}

.form-group input,
.form-group select,
.form-group textarea {
    padding: var(--space-3) var(--space-4);
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    color: var(--color-text);
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    outline: none;
    transition: all var(--transition-base);
}

.form-group input::placeholder,
.form-group textarea::placeholder {
    color: var(--color-text-muted);
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

.form-group select {
    cursor: pointer;
}

.form-group select option {
    background: var(--color-bg-secondary);
    color: var(--color-text);
}

.form-hint {
    font-size: var(--font-size-xs);
    color: var(--color-text-muted);
}

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-4);
}

/* ============================================
   Modal Base
   ============================================ */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.8);
    backdrop-filter: blur(8px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 200;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
    padding: var(--space-4);
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    position: relative;
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-2xl);
    max-width: 600px;
    width: 100%;
    max-height: 90vh;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    transform: scale(0.95) translateY(10px);
    transition: all var(--transition-base);
}

.modal-overlay.active .modal {
    transform: scale(1) translateY(0);
}

.modal-close {
    position: absolute;
    top: var(--space-4);
    right: var(--space-4);
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    color: var(--color-text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
    z-index: 10;
}

.modal-close svg {
    pointer-events: none;
}

.modal-close:hover {
    background: var(--color-bg-card);
    color: var(--color-text);
}

.modal-header {
    padding: var(--space-6);
    border-bottom: 1px solid var(--color-border);
}

.modal-body {
    padding: var(--space-6);
    overflow-y: auto;
    flex: 1;
}

.modal-footer {
    display: flex;
    gap: var(--space-3);
    justify-content: flex-end;
    padding: var(--space-4) var(--space-6);
    border-top: 1px solid var(--color-border);
    background: var(--color-bg-tertiary);
}

/* ============================================
   Toast Notification
   ============================================ */
.toast {
    position: fixed;
    bottom: var(--space-8);
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-4) var(--space-6);
    background: var(--color-success);
    color: var(--color-text);
    border-radius: var(--radius-xl);
    font-weight: 500;
    box-shadow: var(--shadow-xl);
    z-index: 300;
    opacity: 0;
    transition: all var(--transition-base);
}

.toast.show {
    transform: translateX(-50%) translateY(0);
    opacity: 1;
}

.toast.error {
    background: var(--color-error);
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 768px) {
    .header {
        padding: var(--space-3) var(--space-4);
    }

    .nav-links {
        gap: var(--space-1);
    }

    .nav-link {
        padding: var(--space-2);
        font-size: var(--font-size-xs);
    }

    .logo {
        font-size: var(--font-size-lg);
    }

    .logo-icon svg {
        width: 24px;
        height: 24px;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

    h1 {
        font-size: var(--font-size-3xl);
    }

    h2 {
        font-size: var(--font-size-2xl);
    }
}

@media (max-width: 480px) {
    .lang-switcher {
        display: none;
    }

    .nav-link {
        padding: var(--space-2) var(--space-2);
    }
}