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

:root {
    --bg: #0f0f0f;
    --surface: #1a1a2e;
    --accent: #e94560;
    --text: #eee;
    --muted: #888;
    --input-bg: #16213e;
    --success: #4ecca3;
    --error: #e94560;
    --radius: 10px;
}

body {
    background-color: var(--bg);
    color: var(--text);
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, sans-serif;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: stretch;
    padding: 20px;
}

.card {
    background: var(--surface);
    border-radius: 16px;
    padding: 40px;
    width: 100%;
    max-width: 720px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.4);
    display: flex;
    flex-direction: column;
}

header {
    margin-bottom: 32px;
}

h1 {
    font-size: 1.6rem;
    font-weight: 700;
    letter-spacing: -0.02em;
}

.tagline {
    color: var(--muted);
    font-size: 0.9rem;
    margin-top: 6px;
}

/* Input row */
.input-row {
    display: flex;
    gap: 10px;
}

.input-row input {
    flex: 1;
    background: var(--input-bg);
    border: 1px solid transparent;
    color: var(--text);
    padding: 12px 16px;
    border-radius: var(--radius);
    font-size: 0.95rem;
    outline: none;
    transition: border-color 0.2s;
}

.input-row input:focus {
    border-color: var(--accent);
}

.input-row input::placeholder {
    color: var(--muted);
}

#convertBtn {
    background: var(--accent);
    color: #fff;
    border: none;
    padding: 12px 24px;
    border-radius: var(--radius);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: opacity 0.2s;
    white-space: nowrap;
    position: relative;
    min-width: 100px;
}

#convertBtn:hover {
    opacity: 0.85;
}

#convertBtn:disabled {
    cursor: not-allowed;
    opacity: 0.7;
}

#convertBtn.loading .btn-label {
    visibility: hidden;
}

#convertBtn.loading .btn-spinner {
    display: block;
}

.btn-spinner {
    display: none;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 18px;
    height: 18px;
    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: translate(-50%, -50%) rotate(360deg); }
}

/* Error */
.error {
    background: rgba(233, 69, 96, 0.12);
    color: var(--error);
    padding: 10px 16px;
    border-radius: var(--radius);
    font-size: 0.85rem;
    margin-top: 12px;
}

/* Output section */
.output-section {
    margin-top: 24px;
    flex: 1;
    display: flex;
    flex-direction: column;
    min-height: 0;
}

.output-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 10px;
}

.tab-bar {
    display: flex;
    gap: 4px;
}

.tab {
    background: none;
    border: none;
    color: var(--muted);
    padding: 6px 14px;
    border-radius: 6px;
    font-size: 0.82rem;
    cursor: pointer;
    transition: color 0.2s, background 0.2s;
}

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

.tab.active {
    background: var(--input-bg);
    color: var(--text);
}

.copy-btn {
    display: flex;
    align-items: center;
    gap: 6px;
    background: none;
    border: 1px solid rgba(255, 255, 255, 0.1);
    color: var(--muted);
    padding: 6px 12px;
    border-radius: 6px;
    font-size: 0.82rem;
    cursor: pointer;
    transition: color 0.2s, border-color 0.2s;
}

.copy-btn:hover {
    color: var(--text);
    border-color: rgba(255, 255, 255, 0.25);
}

.copy-btn.copied {
    color: var(--success);
    border-color: var(--success);
}

#output {
    width: 100%;
    flex: 1;
    min-height: 0;
    background: var(--input-bg);
    color: var(--text);
    border: none;
    padding: 16px;
    border-radius: var(--radius);
    font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
    font-size: 0.85rem;
    line-height: 1.6;
    resize: none;
    outline: none;
    overflow: auto;
}

#output::placeholder {
    color: var(--muted);
}

.preview-pane {
    background: var(--input-bg);
    padding: 20px;
    border-radius: var(--radius);
    font-size: 0.9rem;
    line-height: 1.7;
    flex: 1;
    min-height: 0;
    overflow: auto;
}

.preview-pane h1, .preview-pane h2, .preview-pane h3 {
    margin-top: 1em;
    margin-bottom: 0.4em;
}

.preview-pane h1 { font-size: 1.4rem; }
.preview-pane h2 { font-size: 1.15rem; }

.preview-pane p {
    margin-bottom: 0.6em;
}

.preview-pane hr {
    border: none;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    margin: 1.2em 0;
}

.preview-pane strong {
    color: var(--accent);
}

.preview-pane a {
    color: var(--success);
}

.preview-pane blockquote {
    border-left: 3px solid var(--accent);
    padding-left: 12px;
    color: var(--muted);
    margin: 0.6em 0;
}

.preview-pane code {
    background: rgba(255, 255, 255, 0.06);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.85em;
}

.preview-pane pre {
    background: rgba(0, 0, 0, 0.3);
    padding: 12px;
    border-radius: 6px;
    overflow-x: auto;
    margin: 0.6em 0;
}

.preview-pane pre code {
    background: none;
    padding: 0;
}

/* Toast */
.toast {
    position: fixed;
    bottom: 32px;
    left: 50%;
    transform: translateX(-50%) translateY(20px);
    background: var(--success);
    color: #0f0f0f;
    padding: 10px 24px;
    border-radius: 8px;
    font-size: 0.85rem;
    font-weight: 600;
    opacity: 0;
    transition: opacity 0.25s, transform 0.25s;
    pointer-events: none;
}

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

/* Responsive */
@media (max-width: 540px) {
    body {
        padding: 24px 12px;
    }

    .card {
        padding: 24px 18px;
    }

    .input-row {
        flex-direction: column;
    }

    #convertBtn {
        width: 100%;
    }

    h1 {
        font-size: 1.3rem;
    }
}