:root {
    --bg: #0d1117;
    --surface: #161b22;
    --surface2: #1e2530;
    --border: #30363d;
    --border-focus: #58a6ff;
    --accent: #238636;
    --accent-hover: #2ea043;
    --accent-btn: #1f6feb;
    --accent-btn-h: #388bfd;
    --text: #c9d1d9;
    --text-dim: #8b949e;
    --text-bright: #f0f6fc;
    --err-bg: #160b0b;
    --err-border: #6e1818;
    --err-text: #f85149;
    --ok-bg: #0b1b0f;
    --ok-border: #196127;
    --ok-text: #3fb950;
    --warn-bg: #1c1507;
    --warn-border: #6e4c0e;
    --warn-text: #d29922;
    --radius: 8px;
    --mono: 'JetBrains Mono', 'Cascadia Code', 'Fira Code', 'Consolas', monospace;
}

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

body {
    background: var(--bg);
    color: var(--text);
    font-family: -apple-system, 'Segoe UI', system-ui, sans-serif;
    font-size: 14px;
    line-height: 1.5;
    min-height: 100vh;
    padding: 32px 16px 64px;
}

.page {
    max-width: 900px;
    margin: 0 auto;
}

/* ── Header ── */
.header {
    margin-bottom: 28px;
}

.header h1 {
    font-size: 22px;
    font-weight: 700;
    color: var(--text-bright);
    letter-spacing: -0.02em;
    display: flex;
    align-items: center;
    gap: 10px;
}

.header h1 .arrow {
    color: var(--text-dim);
    font-weight: 300;
}

.header h1 .brand {
    color: #58a6ff;
}

.header p {
    margin-top: 6px;
    color: var(--text-dim);
    font-size: 13px;
}

/* ── Card ── */
.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 20px;
    margin-bottom: 14px;
}

/* ── Label ── */
.field-label {
    display: block;
    font-size: 11px;
    font-weight: 600;
    color: var(--text-dim);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 8px;
    user-select: none;
}

/* ── Textarea ── */
textarea {
    width: 100%;
    background: var(--surface2);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    color: var(--text);
    font-family: var(--mono);
    font-size: 12.5px;
    line-height: 1.55;
    padding: 12px 14px;
    resize: vertical;
    outline: none;
    transition: border-color 0.15s;
    word-break: break-all;
}

textarea:focus {
    border-color: var(--border-focus);
}

textarea::placeholder {
    color: var(--text-dim);
    opacity: 0.55;
}

#key-input {
    min-height: 110px;
}

#output {
    min-height: 420px;
}

/* ── Buttons ── */
.btn-row {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 12px;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 7px 16px;
    border-radius: var(--radius);
    border: 1px solid transparent;
    cursor: pointer;
    font-size: 13px;
    font-weight: 600;
    transition: background 0.15s, border-color 0.15s, color 0.15s, transform 0.1s;
    user-select: none;
    white-space: nowrap;
}

.btn:active {
    transform: scale(0.97);
}

.btn-primary {
    background: var(--accent-btn);
    color: #fff;
    border-color: rgba(240, 246, 252, .1);
}

.btn-primary:hover {
    background: var(--accent-btn-h);
}

.btn-ghost {
    background: transparent;
    color: var(--text-dim);
    border-color: var(--border);
}

.btn-ghost:hover {
    border-color: var(--text-dim);
    color: var(--text);
}

.btn-copy {
    background: var(--accent);
    color: #fff;
    border-color: rgba(240, 246, 252, .1);
}

.btn-copy:hover {
    background: var(--accent-hover);
}

.btn-copy.copied {
    background: #388bfd33;
    border-color: #388bfd;
    color: #388bfd;
}

/* ── Alerts ── */
.alert {
    display: none;
    border-radius: var(--radius);
    padding: 11px 16px;
    font-size: 13px;
    margin-bottom: 14px;
    gap: 10px;
    align-items: flex-start;
    line-height: 1.5;
}

.alert.show {
    display: flex;
}

.alert-icon {
    flex-shrink: 0;
    font-size: 15px;
    margin-top: 1px;
}

.alert-body {
    flex: 1;
}

.alert-title {
    font-weight: 600;
    margin-bottom: 2px;
}

.alert-detail {
    color: inherit;
    opacity: 0.85;
    font-family: var(--mono);
    font-size: 11.5px;
    word-break: break-word;
}

.alert-error {
    background: var(--err-bg);
    border: 1px solid var(--err-border);
    color: var(--err-text);
}

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

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

/* ── Output header ── */
.output-bar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 10px;
    flex-wrap: wrap;
    gap: 8px;
}

.output-bar .field-label {
    margin-bottom: 0;
}

.badge {
    font-size: 11px;
    padding: 2px 10px;
    border-radius: 20px;
    background: var(--surface2);
    border: 1px solid var(--border);
    color: var(--text-dim);
}

/* ── Output section ── */
#output-section {
    display: none;
}

#output-section.show {
    display: block;
}

/* ── Hint ── */
.hint {
    font-size: 12px;
    color: var(--text-dim);
    margin-top: 8px;
    display: flex;
    align-items: center;
    gap: 5px;
}

/* ── Alert close button ── */
.alert-close {
    flex-shrink: 0;
    background: none;
    border: none;
    cursor: pointer;
    color: inherit;
    opacity: 0.5;
    font-size: 13px;
    padding: 2px 4px;
    line-height: 1;
    border-radius: 4px;
    transition: opacity 0.15s;
    align-self: flex-start;
    margin-left: 4px;
}

.alert-close:hover {
    opacity: 1;
}

/* ── Divider ── */
.divider {
    border: none;
    border-top: 1px solid var(--border);
    margin: 4px 0 14px;
}

/* ── GitHub link ── */
.gh-link {
    display: block;
    margin: 40px auto 20px;
    width: fit-content;
    position: relative;
    color: var(--text-dim);
}

.gh-link:hover {
    color: var(--text-bright);
}

.page {
    position: relative;
}

@media (max-width: 520px) {
    body {
        padding: 20px 12px 64px;
    }

    .header h1 {
        font-size: 18px;
    }

    .btn {
        font-size: 12px;
        padding: 6px 12px;
    }

    .gh-link {
        bottom: 16px;
    }
}