/* ==========================================================================
   ShareDrop - Modern Design System & Global Styles
   ========================================================================== */

:root {
    /* Brand Palette - Light Theme (Default) */
    --color-primary: #4f46e5;
    --color-primary-hover: #4338ca;
    --color-primary-light: #eef2ff;
    --color-primary-glow: rgba(79, 70, 229, 0.25);
    
    --color-secondary: #0ea5e9;
    --color-secondary-hover: #0284c7;
    --color-secondary-light: #e0f2fe;

    --color-accent: #10b981;
    --color-accent-hover: #059669;
    --color-accent-light: #ecfdf5;

    --color-warning: #f59e0b;
    --color-danger: #ef4444;
    --color-danger-light: #fee2e2;

    /* Neutrals - Light Theme */
    --bg-page: #f8fafc;
    --bg-surface: #ffffff;
    --bg-surface-elevated: #ffffff;
    --bg-surface-sunken: #f1f5f9;
    --bg-glass: rgba(255, 255, 255, 0.85);
    --border-color: #e2e8f0;
    --border-color-hover: #cbd5e1;
    --border-color-focus: #4f46e5;

    /* Text Colors */
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #64748b;
    --text-on-primary: #ffffff;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.08), 0 2px 4px -2px rgba(0, 0, 0, 0.04);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.03);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.04);
    --shadow-glow: 0 0 25px var(--color-primary-glow);

    /* Radii */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;

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

    /* Layout */
    --max-width: 1160px;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

/* ==========================================================================
   Dark Theme Overrides
   ========================================================================== */
[data-theme="dark"] {
    --color-primary: #6366f1;
    --color-primary-hover: #4f46e5;
    --color-primary-light: rgba(99, 102, 241, 0.15);
    --color-primary-glow: rgba(99, 102, 241, 0.35);

    --color-secondary: #38bdf8;
    --color-secondary-hover: #0ea5e9;
    --color-secondary-light: rgba(56, 189, 248, 0.15);

    --color-accent: #34d399;
    --color-accent-hover: #10b981;
    --color-accent-light: rgba(52, 211, 153, 0.15);

    /* Neutrals - Dark Theme */
    --bg-page: #0b0f19;
    --bg-surface: #111827;
    --bg-surface-elevated: #1e293b;
    --bg-surface-sunken: #070a11;
    --bg-glass: rgba(17, 24, 39, 0.85);
    --border-color: #1f293d;
    --border-color-hover: #334155;
    --border-color-focus: #6366f1;

    /* Text Colors */
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    --text-on-primary: #ffffff;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.4);
    --shadow-md: 0 4px 8px -1px rgba(0, 0, 0, 0.5), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 12px 20px -3px rgba(0, 0, 0, 0.6), 0 4px 6px -4px rgba(0, 0, 0, 0.4);
    --shadow-xl: 0 24px 30px -5px rgba(0, 0, 0, 0.7), 0 10px 10px -6px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 30px rgba(99, 102, 241, 0.4);
}

/* Base Resets */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-sans);
    background-color: var(--bg-page);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: background-color var(--transition-normal), color var(--transition-normal);
    overflow-x: hidden;
}

/* Background Ambient Glow */
.ambient-bg {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    pointer-events: none;
    z-index: 0;
    background: 
        radial-gradient(circle at 15% 15%, rgba(79, 70, 229, 0.08) 0%, transparent 40%),
        radial-gradient(circle at 85% 85%, rgba(14, 165, 233, 0.08) 0%, transparent 40%);
}

[data-theme="dark"] .ambient-bg {
    background: 
        radial-gradient(circle at 15% 15%, rgba(99, 102, 241, 0.12) 0%, transparent 45%),
        radial-gradient(circle at 85% 85%, rgba(56, 189, 248, 0.1) 0%, transparent 45%);
}

/* Main Container */
.container {
    width: 100%;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 20px;
    position: relative;
    z-index: 1;
}

/* ==========================================================================
   Header & Navigation
   ========================================================================== */
.site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: var(--bg-glass);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
    transition: all var(--transition-normal);
}

.nav-wrap {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 70px;
}

.brand-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 800;
    font-size: 1.35rem;
    letter-spacing: -0.02em;
}

.brand-icon {
    width: 38px;
    height: 38px;
    background: linear-gradient(135deg, var(--color-primary), var(--color-secondary));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: #ffffff;
    box-shadow: 0 4px 12px var(--color-primary-glow);
    transition: transform var(--transition-fast);
}

.brand-logo:hover .brand-icon {
    transform: rotate(-5deg) scale(1.05);
}

.brand-text span {
    color: var(--color-primary);
}

.header-controls {
    display: flex;
    align-items: center;
    gap: 12px;
}

/* Language & Theme Selectors */
.control-btn, .lang-select {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    background-color: var(--bg-surface);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    padding: 8px 12px;
    border-radius: var(--radius-full);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    font-family: inherit;
    outline: none;
}

.control-btn:hover, .lang-select:hover {
    color: var(--text-primary);
    border-color: var(--border-color-hover);
    background-color: var(--bg-surface-sunken);
}

.theme-toggle-btn {
    width: 40px;
    height: 40px;
    padding: 0;
    border-radius: 50%;
}

.theme-toggle-btn svg {
    width: 20px;
    height: 20px;
    transition: transform var(--transition-normal);
}

.theme-toggle-btn:hover svg {
    transform: rotate(20deg);
}

/* ==========================================================================
   Hero Section
   ========================================================================== */
.hero-section {
    padding: 48px 0 24px;
    text-align: center;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 6px 14px;
    background: var(--color-primary-light);
    color: var(--color-primary);
    border: 1px solid rgba(79, 70, 229, 0.2);
    border-radius: var(--radius-full);
    font-size: 0.8125rem;
    font-weight: 600;
    margin-bottom: 20px;
}

.hero-title {
    font-size: clamp(2rem, 4.5vw, 3.25rem);
    font-weight: 800;
    line-height: 1.15;
    letter-spacing: -0.03em;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.hero-title .gradient-text {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero-subtitle {
    font-size: clamp(1rem, 2vw, 1.15rem);
    color: var(--text-secondary);
    max-width: 680px;
    margin: 0 auto;
    line-height: 1.6;
}

/* ==========================================================================
   Tabs Navigation (3 Tools)
   ========================================================================== */
.tools-nav-container {
    margin: 32px 0 28px;
    display: flex;
    justify-content: center;
}

.tools-nav {
    display: inline-flex;
    background-color: var(--bg-surface-sunken);
    padding: 6px;
    border-radius: var(--radius-full);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    gap: 6px;
    max-width: 100%;
    overflow-x: auto;
}

.tool-tab {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 22px;
    border-radius: var(--radius-full);
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: 0.9375rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
    outline: none;
}

.tool-tab svg {
    width: 18px;
    height: 18px;
    transition: transform var(--transition-fast);
}

.tool-tab:hover {
    color: var(--text-primary);
}

.tool-tab.active {
    background-color: var(--bg-surface);
    color: var(--color-primary);
    box-shadow: var(--shadow-md);
}

.tool-tab.active svg {
    transform: scale(1.1);
}

/* ==========================================================================
   Main Application Body & Cards
   ========================================================================== */
.app-content {
    margin-bottom: 60px;
}

.tab-pane {
    display: none;
    animation: fadeIn 0.3s ease-in-out;
}

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

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(6px); }
    to { opacity: 1; transform: translateY(0); }
}

.card {
    background-color: var(--bg-surface);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: 32px;
    box-shadow: var(--shadow-lg);
    transition: box-shadow var(--transition-normal), border-color var(--transition-normal);
}

.card-header {
    margin-bottom: 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 12px;
}

.card-title {
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 10px;
}

.card-subtitle {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    margin-top: 4px;
}

/* Responsive Grid Split for Send / Receive */
.split-grid {
    display: grid;
    grid-template-columns: 1.15fr 0.85fr;
    gap: 28px;
}

@media (max-width: 900px) {
    .split-grid {
        grid-template-columns: 1fr;
    }
}

/* ==========================================================================
   Footer
   ========================================================================== */
.site-footer {
    margin-top: auto;
    border-top: 1px solid var(--border-color);
    background-color: var(--bg-surface);
    padding: 40px 0 28px;
    font-size: 0.875rem;
    color: var(--text-muted);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 20px;
}

.footer-links {
    display: flex;
    gap: 20px;
    list-style: none;
}

.footer-links a {
    color: var(--text-muted);
    text-decoration: none;
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: var(--color-primary);
}