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

html, body {
    height: 100%;
    background: #0d1117;
    color: #c9d1d9;
    font-family: 'Courier New', Courier, monospace;
    font-size: 13px;
    line-height: 1.6;
}

.back-link {
    position: fixed;
    top: 12px;
    left: 16px;
    z-index: 10;
    color: #8b949e;
    font-family: 'Courier New', Courier, monospace;
    font-size: 12px;
    text-decoration: none;
    padding: 4px 8px;
    border: 1px solid #21262d;
    border-radius: 4px;
    background: rgba(13, 17, 23, 0.85);
}

.back-link:hover {
    color: #3fb950;
    border-color: #3fb950;
}

#app {
    display: flex;
    flex-direction: column;
    height: 100vh;
    max-width: 1200px;
    margin: 0 auto;
    padding: 40px 20px 12px;
}

#output {
    flex: 1;
    overflow-y: auto;
    overflow-x: auto;
    white-space: pre;
    padding-bottom: 8px;
}

#input-row {
    display: none;
    align-items: center;
    gap: 10px;
    border-top: 1px solid #21262d;
    padding-top: 10px;
    margin-top: 6px;
    flex-shrink: 0;
}

.prompt {
    color: #3fb950;
    font-size: 18px;
    font-weight: bold;
    line-height: 1;
    user-select: none;
}

#vat-input {
    flex: 1;
    background: transparent;
    border: none;
    color: #3fb950;
    font-family: inherit;
    font-size: inherit;
    outline: none;
    caret-color: #3fb950;
}

#vat-input::placeholder {
    color: #30363d;
}

/* Scrollbar */
#output::-webkit-scrollbar { width: 5px; height: 5px; }
#output::-webkit-scrollbar-track { background: transparent; }
#output::-webkit-scrollbar-thumb { background: #30363d; border-radius: 3px; }

@media (max-width: 768px) {
    html, body { font-size: 11px; }
    #app { padding: 34px 12px 8px; }
    .back-link { font-size: 11px; top: 8px; left: 10px; }
}