:root {
    --bg-body: radial-gradient(circle at top, #1f2937 0%, #020617 45%, #020617 100%);
    --bg-header: rgba(15, 23, 42, 0.9);
    --text-primary: #e5e7eb;
    --text-secondary: #9ca3af;
    --text-muted: #cbd5f5;
    --accent-from: #6366f1;
    --accent-to: #4f46e5;
    --card-bg: rgba(15, 23, 42, 0.98);
    --card-border: rgba(148, 163, 184, 0.35);
    --input-bg: rgba(15, 23, 42, 0.95);
    --input-border: rgba(148, 163, 184, 0.5);
    --section-border: rgba(148, 163, 184, 0.25);
    --footer-bg: #020617;
    --btn-secondary-bg: transparent;
    --btn-secondary-border: rgba(148, 163, 184, 0.7);
    --btn-secondary-text: #e5e7eb;
    --feature-card-bg: radial-gradient(circle at top left, rgba(30, 64, 175, 0.45), rgba(15, 23, 42, 0.98));
    --shadow-color: rgba(15, 23, 42, 0.9);
}

[data-theme="light"] {
    --bg-body: linear-gradient(180deg, #f8fafc 0%, #e2e8f0 50%, #cbd5e1 100%);
    --bg-header: rgba(248, 250, 252, 0.95);
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #334155;
    --accent-from: #6366f1;
    --accent-to: #4f46e5;
    --card-bg: rgba(255, 255, 255, 0.98);
    --card-border: rgba(148, 163, 184, 0.5);
    --input-bg: rgba(255, 255, 255, 0.95);
    --input-border: rgba(100, 116, 139, 0.5);
    --section-border: rgba(148, 163, 184, 0.35);
    --footer-bg: #0f172a;
    --btn-secondary-bg: transparent;
    --btn-secondary-border: rgba(71, 85, 105, 0.7);
    --btn-secondary-text: #0f172a;
    --feature-card-bg: linear-gradient(135deg, rgba(255, 255, 255, 0.95) 0%, rgba(241, 245, 249, 0.98) 100%);
    --shadow-color: rgba(15, 23, 42, 0.15);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--bg-body);
    color: var(--text-primary);
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    transition: background 0.3s ease, color 0.3s ease;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    padding: 12px 0;
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    background: var(--bg-header);
    backdrop-filter: blur(18px);
    box-shadow: 0 1px 0 var(--card-border);
    animation: slideDown 0.5s ease;
}

@keyframes slideDown {
    from { transform: translateY(-100%); }
    to { transform: translateY(0); }
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 22px;
    font-weight: 800;
    letter-spacing: -0.03em;
    color: var(--text-primary);
    text-decoration: none;
}

.logo span { color: var(--accent-to); }

.nav-right {
    display: flex;
    align-items: center;
    gap: 12px;
}

.theme-toggle {
    width: 42px;
    height: 42px;
    border-radius: 999px;
    border: 1px solid var(--btn-secondary-border);
    background: var(--btn-secondary-bg);
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    transition: all 0.25s ease;
}

.theme-toggle:hover {
    background: rgba(148, 163, 184, 0.15);
}

.btn {
    padding: 10px 24px;
    border: none;
    border-radius: 999px;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.25s ease;
    text-decoration: none;
    display: inline-block;
    letter-spacing: 0.02em;
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent-from) 0%, var(--accent-to) 100%);
    color: #f9fafb;
    box-shadow: 0 18px 45px var(--shadow-color);
}

.btn-primary:hover {
    transform: translateY(-1px);
    box-shadow: 0 22px 55px var(--shadow-color);
    filter: brightness(1.05);
}

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

.btn-secondary:hover {
    background: rgba(148, 163, 184, 0.12);
    transform: translateY(-1px);
}

/* Hero – main focus: shorten form */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 100px 20px 60px;
    text-align: center;
    animation: fadeInUp 0.8s ease;
}

@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(30px); }
    to { opacity: 1; transform: translateY(0); }
}

.hero h1 {
    font-size: 48px;
    font-weight: 800;
    margin-bottom: 12px;
    line-height: 1.1;
    letter-spacing: -0.03em;
}

.hero .tagline {
    font-size: 18px;
    color: var(--text-secondary);
    margin-bottom: 40px;
    max-width: 520px;
    margin-left: auto;
    margin-right: auto;
}

.shorten-card {
    background: var(--card-bg);
    border-radius: 24px;
    padding: 40px 36px;
    max-width: 620px;
    margin: 0 auto;
    box-shadow: 0 30px 80px var(--shadow-color);
    border: 1px solid var(--card-border);
    animation: fadeInScale 0.8s ease 0.2s backwards;
}

@keyframes fadeInScale {
    from { opacity: 0; transform: scale(0.95); }
    to { opacity: 1; transform: scale(1); }
}

.shorten-form {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.shorten-form input[type="url"] {
    width: 100%;
    padding: 16px 20px;
    font-size: 16px;
    border-radius: 14px;
    border: 1px solid var(--input-border);
    background: var(--input-bg);
    color: var(--text-primary);
    outline: none;
    transition: border-color 0.2s ease;
}

.shorten-form input[type="url"]::placeholder {
    color: var(--text-secondary);
}

.shorten-form input[type="url"]:focus {
    border-color: var(--accent-to);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.2);
}

.shorten-form .btn-submit {
    width: 100%;
    padding: 16px;
    font-size: 17px;
    background: linear-gradient(135deg, var(--accent-from) 0%, var(--accent-to) 100%);
    color: #f9fafb;
    border: none;
    border-radius: 14px;
    cursor: pointer;
    font-weight: 600;
    letter-spacing: 0.04em;
    transition: all 0.25s ease;
}

.shorten-form .btn-submit:hover {
    transform: translateY(-1px);
    box-shadow: 0 18px 45px var(--shadow-color);
    filter: brightness(1.05);
}

.short-url-result {
    margin-top: 24px;
    padding: 0;
    background: transparent;
    border-radius: 16px;
    text-align: left;
    display: none;
    overflow: hidden;
}

.short-url-result.visible {
    display: block;
    animation: shortUrlReveal 0.4s cubic-bezier(0.22, 1, 0.36, 1) forwards;
}

@keyframes shortUrlReveal {
    from {
        opacity: 0;
        transform: translateY(-8px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.short-url-result .result-inner {
    padding: 20px 24px;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.08) 0%, rgba(79, 70, 229, 0.05) 100%);
    border-radius: 16px;
    border: 1px solid rgba(99, 102, 241, 0.35);
    box-shadow: 0 4px 24px rgba(15, 23, 42, 0.4);
}

[data-theme="light"] .short-url-result .result-inner {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.06) 0%, rgba(79, 70, 229, 0.04) 100%);
    border-color: rgba(99, 102, 241, 0.4);
    box-shadow: 0 4px 20px rgba(15, 23, 42, 0.08);
}

.short-url-result label {
    display: block;
    font-size: 11px;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: 10px;
}

.short-url-result .url-row {
    display: flex;
    align-items: center;
    gap: 12px;
    flex-wrap: wrap;
    margin-top: 4px;
}

.short-url-result a {
    flex: 1;
    min-width: 0;
    padding: 12px 16px;
    background: var(--input-bg);
    border-radius: 10px;
    border: 1px solid var(--card-border);
    color: var(--accent-to);
    font-weight: 600;
    font-size: 15px;
    word-break: break-all;
    text-decoration: none;
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.short-url-result a:hover {
    border-color: rgba(99, 102, 241, 0.5);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

.short-url-result .copy-btn {
    flex-shrink: 0;
    padding: 12px 20px;
    font-size: 14px;
    font-weight: 600;
    border-radius: 10px;
    border: 1px solid var(--accent-to);
    background: linear-gradient(135deg, var(--accent-from) 0%, var(--accent-to) 100%);
    color: #fff;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.short-url-result .copy-btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
}

/* Section common */
section.section {
    padding: 80px 0;
    border-top: 1px solid var(--section-border);
}

section.section h2 {
    text-align: center;
    font-size: 36px;
    font-weight: 800;
    color: var(--text-primary);
    margin-bottom: 40px;
    letter-spacing: -0.02em;
}

/* How it works */
.how-steps {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 32px;
    max-width: 900px;
    margin: 0 auto;
}

.how-step {
    text-align: center;
    padding: 28px 24px;
    border-radius: 20px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
}

.how-step .num {
    width: 48px;
    height: 48px;
    margin: 0 auto 16px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--accent-from), var(--accent-to));
    color: #fff;
    font-weight: 800;
    font-size: 18px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.how-step h3 {
    font-size: 18px;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.how-step p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Features */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 32px;
}

.feature-card {
    padding: 32px 28px;
    border-radius: 20px;
    background: var(--feature-card-bg);
    border: 1px solid var(--card-border);
    transition: all 0.3s ease;
    box-shadow: 0 24px 70px var(--shadow-color);
}

.feature-card:hover {
    transform: translateY(-4px);
    border-color: rgba(191, 219, 254, 0.6);
}

.feature-icon {
    font-size: 36px;
    margin-bottom: 16px;
}

.feature-card h3 {
    font-size: 20px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 10px;
}

.feature-card p {
    font-size: 15px;
    color: var(--text-muted);
    line-height: 1.7;
}

/* Pricing */
.pricing-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 32px;
    max-width: 900px;
    margin: 0 auto;
}

.pricing-card {
    padding: 36px 32px;
    border-radius: 20px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    text-align: center;
}

.pricing-card.featured {
    border-color: var(--accent-to);
    box-shadow: 0 0 0 2px rgba(79, 70, 229, 0.3);
}

.pricing-card h3 {
    font-size: 22px;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.pricing-card .price {
    font-size: 36px;
    font-weight: 800;
    color: var(--accent-to);
    margin-bottom: 20px;
}

.pricing-card ul {
    list-style: none;
    text-align: left;
    color: var(--text-secondary);
    font-size: 15px;
    line-height: 2;
}

/* Contact */
.contact-inner {
    max-width: 560px;
    margin: 0 auto;
    text-align: center;
}

.contact-inner p {
    color: var(--text-secondary);
    margin-bottom: 24px;
    font-size: 16px;
}

.contact-inner a {
    color: var(--accent-to);
    font-weight: 600;
}

/* Login section (CTA) */
.login-cta {
    text-align: center;
    padding: 60px 0;
}

.login-cta h2 {
    margin-bottom: 16px;
}

.login-cta p {
    color: var(--text-secondary);
    margin-bottom: 28px;
    font-size: 18px;
}

.login-cta .cta-buttons {
    display: flex;
    gap: 16px;
    justify-content: center;
    flex-wrap: wrap;
}

/* Footer */
footer {
    background: var(--footer-bg);
    color: #9ca3af;
    padding: 32px 0;
    text-align: center;
    border-top: 1px solid var(--section-border);
}

footer p {
    opacity: 0.9;
    font-size: 14px;
}

@media (max-width: 768px) {
    .hero h1 { font-size: 32px; }
    .hero .tagline { font-size: 16px; }
    .shorten-card { padding: 28px 20px; }
    .nav-right {
        flex-wrap: wrap;
        justify-content: flex-end;
        gap: 8px;
    }
    .btn { padding: 8px 16px; font-size: 14px; }
    .theme-toggle { width: 38px; height: 38px; font-size: 16px; }
    section.section h2 { font-size: 28px; }
    .shorten-form {
        flex-direction: column;
    }
}