/* ===== CSS Variables & Reset ===== */
:root {
    --bg-primary: #060d13;
    --bg-secondary: #0c1a25;
    --bg-card: rgba(10, 25, 40, 0.75);
    --border-color: rgba(20, 184, 166, 0.18);
    --text-primary: #e2f1f8;
    --text-secondary: #7da8be;
    --accent: #14b8a6;
    --accent-glow: rgba(20, 184, 166, 0.35);
    --accent-light: #5eead4;
    --gradient-start: #0d9488;
    --gradient-end: #06b6d4;
    --success: #34d399;
    --error: #f87171;
    --radius: 14px;
    --radius-sm: 8px;
    --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow-x: hidden;
    padding: 2rem 1rem;
}

/* ===== Animated Background ===== */
.bg-particles {
    position: fixed; inset: 0;
    z-index: 0; pointer-events: none;
    background:
        radial-gradient(ellipse 600px 400px at 20% 30%, rgba(20,184,166,0.07), transparent),
        radial-gradient(ellipse 500px 500px at 80% 70%, rgba(6,182,212,0.06), transparent);
}

.bg-particles::before {
    content: '';
    position: absolute; inset: 0;
    background-image:
        radial-gradient(1.5px 1.5px at 10% 20%, rgba(94,234,212,0.25), transparent),
        radial-gradient(1px 1px at 30% 60%, rgba(6,182,212,0.2), transparent),
        radial-gradient(1.5px 1.5px at 70% 30%, rgba(20,184,166,0.25), transparent),
        radial-gradient(1px 1px at 90% 80%, rgba(94,234,212,0.15), transparent),
        radial-gradient(1px 1px at 50% 50%, rgba(6,182,212,0.12), transparent);
    animation: drift 20s ease-in-out infinite alternate;
}

@keyframes drift {
    0% { transform: translate(0, 0) scale(1); }
    100% { transform: translate(-20px, 15px) scale(1.05); }
}

/* ===== Layout ===== */
.container {
    position: relative; z-index: 1;
    width: 100%; max-width: 560px;
}

/* ===== Header ===== */
.header { text-align: center; margin-bottom: 2rem; }

.logo {
    display: flex; align-items: center; justify-content: center; gap: 0.75rem;
    margin-bottom: 0.75rem;
}

.logo-icon {
    width: 42px; height: 42px; padding: 8px;
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    border-radius: 12px; color: #fff;
    box-shadow: 0 4px 20px var(--accent-glow);
}
.logo-icon svg { width: 100%; height: 100%; }

.header h1 {
    font-size: 2.2rem; font-weight: 800; letter-spacing: -1px;
}
.accent { color: var(--accent-light); }

.tagline {
    color: var(--text-secondary); font-size: 0.95rem; font-weight: 300;
}

/* ===== Main Card ===== */
.main-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 2rem;
    backdrop-filter: blur(24px);
    box-shadow: 0 8px 40px rgba(0,0,0,0.35), inset 0 1px 0 rgba(255,255,255,0.05);
}

/* ===== Form ===== */
.input-label {
    display: flex; align-items: center; gap: 6px;
    font-size: 0.8rem; font-weight: 600; text-transform: uppercase;
    letter-spacing: 0.5px; color: var(--text-secondary); margin-bottom: 0.5rem;
}

.url-input-wrapper {
    display: flex; gap: 0.5rem;
}

.url-input-wrapper input {
    flex: 1; padding: 0.85rem 1rem;
    background: rgba(255,255,255,0.04);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    color: var(--text-primary); font-size: 0.95rem;
    font-family: inherit;
    transition: border-color var(--transition), box-shadow var(--transition);
    outline: none;
}
.url-input-wrapper input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
}
.url-input-wrapper input::placeholder { color: rgba(255,255,255,0.2); }

/* ===== Generate Button ===== */
.generate-btn {
    display: flex; align-items: center; gap: 0.5rem;
    padding: 0.85rem 1.5rem;
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    border: none; border-radius: var(--radius-sm);
    color: #fff; font-size: 0.9rem; font-weight: 600;
    font-family: inherit; cursor: pointer;
    transition: transform var(--transition), box-shadow var(--transition), opacity var(--transition);
    white-space: nowrap;
}
.generate-btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 6px 24px var(--accent-glow);
}
.generate-btn:active { transform: translateY(0); }
.generate-btn.loading { pointer-events: none; opacity: 0.8; }
.generate-btn.loading .btn-text { display: none; }
.generate-btn.loading .btn-loader { display: block; }

.btn-loader {
    display: none; width: 20px; height: 20px;
    border: 2px solid rgba(255,255,255,0.3);
    border-top-color: #fff; border-radius: 50%;
    animation: spin 0.6s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ===== Options Toggle ===== */
.options-toggle {
    display: flex; align-items: center; gap: 0.5rem;
    width: 100%; padding: 0.75rem 0; margin-top: 1rem;
    background: none; border: none; color: var(--text-secondary);
    font-size: 0.85rem; font-family: inherit; cursor: pointer;
    transition: color var(--transition);
}
.options-toggle:hover { color: var(--accent-light); }
.toggle-chevron {
    margin-left: auto; font-size: 0.7rem;
    transition: transform var(--transition);
}
.options-toggle.open .toggle-chevron { transform: rotate(180deg); }

/* ===== Options Panel ===== */
.options-panel {
    max-height: 0; overflow: hidden;
    transition: max-height 0.4s ease, opacity 0.3s ease;
    opacity: 0;
}
.options-panel.open { max-height: 400px; opacity: 1; }

.options-grid {
    display: grid; grid-template-columns: 1fr 1fr;
    gap: 1.25rem; padding: 1rem 0;
    border-top: 1px solid var(--border-color);
}

.range-input {
    width: 100%; appearance: none; height: 4px;
    background: rgba(255,255,255,0.08); border-radius: 2px;
    outline: none; margin-top: 0.5rem;
}
.range-input::-webkit-slider-thumb {
    appearance: none; width: 16px; height: 16px;
    background: var(--accent); border-radius: 50%; cursor: pointer;
    box-shadow: 0 0 8px var(--accent-glow);
}
.range-value {
    display: inline-block; margin-top: 4px;
    font-size: 0.8rem; color: var(--accent-light); font-weight: 600;
}

.color-picker-wrapper {
    display: flex; align-items: center; gap: 0.5rem; margin-top: 0.5rem;
}
.color-input {
    width: 36px; height: 36px; border: 2px solid var(--border-color);
    border-radius: var(--radius-sm); cursor: pointer;
    background: none; padding: 2px;
}
.color-hex {
    font-size: 0.8rem; color: var(--text-secondary); font-family: monospace;
}

.select-input {
    width: 100%; padding: 0.6rem 0.75rem; margin-top: 0.5rem;
    background: rgba(255,255,255,0.04);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    color: var(--text-primary); font-size: 0.85rem;
    font-family: inherit; outline: none; cursor: pointer;
}
.select-input:focus { border-color: var(--accent); }
.select-input option { background: var(--bg-secondary); }

/* ===== Result Section ===== */
.result-section {
    margin-top: 2rem; text-align: center;
    animation: fadeUp 0.5s ease;
}
.result-section.hidden { display: none; }

@keyframes fadeUp {
    from { opacity: 0; transform: translateY(16px); }
    to { opacity: 1; transform: translateY(0); }
}

.qr-preview {
    display: inline-block; padding: 1.5rem;
    background: #fff; border-radius: var(--radius);
    box-shadow: 0 4px 24px rgba(0,0,0,0.3);
    transition: transform var(--transition);
}
.qr-preview:hover { transform: scale(1.02); }
.qr-preview img { display: block; max-width: 260px; height: auto; }

.result-actions {
    display: flex; justify-content: center; gap: 0.75rem; margin-top: 1.25rem;
}

.action-btn {
    display: flex; align-items: center; gap: 0.4rem;
    padding: 0.65rem 1.2rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: rgba(255,255,255,0.04);
    color: var(--text-primary); font-size: 0.85rem;
    font-family: inherit; cursor: pointer;
    transition: all var(--transition);
}
.action-btn:hover {
    border-color: var(--accent);
    background: rgba(124,92,252,0.1);
}
.action-btn.success {
    border-color: var(--success); color: var(--success);
}

.encoded-url {
    margin-top: 0.75rem; font-size: 0.78rem;
    color: var(--text-secondary); word-break: break-all;
    opacity: 0.7;
}

/* ===== Error ===== */
.error-display {
    display: flex; align-items: center; gap: 0.5rem;
    margin-top: 1rem; padding: 0.75rem 1rem;
    background: rgba(248,113,113,0.1);
    border: 1px solid rgba(248,113,113,0.25);
    border-radius: var(--radius-sm);
    color: var(--error); font-size: 0.85rem;
    animation: fadeUp 0.3s ease;
}
.error-display.hidden { display: none; }

/* ===== Footer ===== */
.footer {
    text-align: center; margin-top: 2rem;
    font-size: 0.8rem; color: var(--text-secondary); opacity: 0.6;
}
.footer a { color: var(--accent-light); text-decoration: none; }
.footer a:hover { text-decoration: underline; }

/* ===== Responsive ===== */
@media (max-width: 500px) {
    .url-input-wrapper { flex-direction: column; }
    .options-grid { grid-template-columns: 1fr; }
    .header h1 { font-size: 1.8rem; }
    .main-card { padding: 1.25rem; }
}