:root {
    --bg-main: #000000;
    --bg-card: #0a0a0a;
    --border: #333333;
    --border-hover: #555555;
    --text-main: #ffffff;
    --text-muted: #888888;
    --accent: #ffffff;
    --font-main: 'Inter', system-ui, -apple-system, sans-serif;
    --font-mono: 'Courier New', monospace;
}

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

body {
    background-color: var(--bg-main);
    color: var(--text-main);
    font-family: var(--font-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 2rem 1rem;
}

/* --- Container --- */
.app-container {
    width: 100%;
    max-width: 1100px;
    display: flex;
    flex-direction: column;
    gap: 3rem;
}

/* --- Header --- */
.app-header {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1.5rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--border);
    width: 100%;
}

.brand h1 {
    font-size: 1.5rem;
    letter-spacing: 0.2em;
    font-weight: 700;
    text-transform: uppercase;
    text-align: center;
}

.mode-toggles {
    display: flex;
    background: var(--bg-card);
    padding: 4px;
    border-radius: 8px;
    border: 1px solid var(--border);
}

.mode-btn {
    background: transparent;
    border: none;
    color: var(--text-muted);
    padding: 8px 20px;
    font-size: 0.85rem;
    cursor: pointer;
    border-radius: 6px;
    font-weight: 600;
    transition: all 0.2s;
}

.mode-btn.active {
    background: var(--text-main);
    color: var(--bg-main);
}

/* --- Transposer Engine Grid --- */
.transposer-engine {
    display: grid;
    grid-template-columns: 1fr 320px 1fr;
    gap: 2rem;
    align-items: start;
}

/* --- IO Cards --- */
.io-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 12px;
    display: flex;
    flex-direction: column;
    height: 500px;
    /* Fixed height for consistency */
    overflow: hidden;
    transition: border 0.2s;
}

.io-card:focus-within {
    border-color: var(--border-hover);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 1.5rem;
    border-bottom: 1px solid var(--border);
    background: #0f0f0f;
}

.card-header h3 {
    font-size: 0.75rem;
    color: var(--text-muted);
    letter-spacing: 0.1em;
    font-weight: 600;
}

.card-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border);
    background: #0f0f0f;
}

/* Input/Output Areas */
textarea {
    flex: 1;
    background: transparent;
    border: none;
    resize: none;
    color: var(--text-main);
    font-family: var(--font-mono);
    font-size: 1.2rem;
    line-height: 1.6;
    padding: 1.5rem;
}

textarea:focus {
    outline: none;
}

.output-display {
    flex: 1;
    background: transparent;
    border: none;
    color: var(--text-main);
    font-family: var(--font-mono);
    font-size: 1.4rem;
    font-weight: bold;
    line-height: 1.8;
    padding: 1.5rem;
    overflow-y: auto;
    white-space: pre-wrap;
    outline: none;
}

/* Highlights */
.chord-span {
    padding: 2px 4px;
    border-radius: 4px;
    transition: 0.1s;
    cursor: pointer;
}

.chord-span:hover {
    background: rgba(255, 255, 255, 0.1);
}

.chord-active {
    background: var(--text-main);
    color: var(--bg-main);
    box-shadow: 0 0 15px rgba(255, 255, 255, 0.4);
    transform: scale(1.05);
    display: inline-block;
}

/* --- Controls Center Column --- */
.engine-controls {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    padding: 1rem 0;
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
    width: 100%;
}

.control-group label {
    font-size: 0.65rem;
    color: var(--text-muted);
    letter-spacing: 0.15em;
    font-weight: 600;
    text-align: center;
    text-transform: uppercase;
}

.control-group.hidden {
    display: none;
}

/* Dials & Buttons */
.dial-display {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: var(--bg-card);
    border: 1px solid var(--border);
    padding: 8px 12px;
    border-radius: 50px;
    height: 44px;
}

.dial-btn,
.mini-btn {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    border: 1px solid var(--border);
    background: transparent;
    color: var(--text-main);
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1rem;
    transition: 0.2s;
}

.dial-btn:hover,
.mini-btn:hover {
    background: var(--text-muted);
    color: #000;
}

.dial-value,
#spd-disp {
    font-family: var(--font-mono);
    font-weight: 700;
    min-width: 40px;
    text-align: center;
}

/* Selectors */
/* Selectors */
.select-wrapper {
    display: flex;
    align-items: center;
    background: var(--bg-card);
    border: 1px solid var(--border);
    padding: 0 12px;
    border-radius: 8px;
    height: 44px;
    position: relative;
    width: 100%;
    transition: all 0.2s ease;
}

.select-wrapper:hover {
    border-color: var(--text-muted);
    background: rgba(255, 255, 255, 0.03);
}

.select-wrapper::after {
    content: '';
    position: absolute;
    right: 12px;
    top: 50%;
    transform: translateY(-50%);
    width: 12px;
    height: 12px;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23888888' stroke-width='3' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-size: contain;
    background-repeat: no-repeat;
    pointer-events: none;
    transition: transform 0.2s;
}

.select-wrapper:focus-within {
    border-color: var(--text-main);
    box-shadow: 0 0 0 1px rgba(255, 255, 255, 0.1);
}

.select-wrapper:focus-within::after {
    transform: translateY(-50%) rotate(180deg);
}

.select-wrapper span {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-right: 8px;
    pointer-events: none;
}

select {
    background: transparent;
    border: none;
    color: var(--text-main);
    font-family: inherit;
    font-size: 0.9rem;
    flex: 1;
    cursor: pointer;
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    height: 100%;
    width: 100%;
    text-align-last: center;
    z-index: 2;
    /* Ensure click */
}

select:focus {
    outline: none;
}

option {
    background-color: var(--bg-card);
    color: var(--text-main);
}

.key-selectors {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    align-items: center;
}

/* Old .arrow removed, replaced by pseudo-element */
.arrow {
    display: none;
}

/* Segmented Control */
.seg-ctrl {
    display: flex;
    width: 100%;
    border: 1px solid var(--border);
    border-radius: 6px;
    overflow: hidden;
    height: 36px;
}

.seg-btn {
    flex: 1;
    background: var(--bg-card);
    border: none;
    color: var(--text-muted);
    border-right: 1px solid var(--border);
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 500;
    transition: background 0.2s;
}

.seg-btn:last-child {
    border-right: none;
}

.seg-btn.active {
    background: var(--text-muted);
    color: #000;
    font-weight: 700;
}

/* Toggles & Tabs */
.toggle-btn {
    background: var(--bg-card);
    border: 1px solid var(--border);
    color: var(--text-muted);
    padding: 12px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
    transition: 0.2s;
}

.toggle-btn.active {
    border-color: var(--text-main);
    color: var(--text-main);
    background: rgba(255, 255, 255, 0.05);
}

.output-tabs {
    display: flex;
    background: #0f0f0f;
    border-bottom: 1px solid var(--border);
}

.tab-btn {
    flex: 1;
    background: transparent;
    border: none;
    color: var(--text-muted);
    padding: 12px;
    cursor: pointer;
    font-size: 0.8rem;
    font-weight: 600;
    border-bottom: 2px solid transparent;
    transition: 0.2s;
}

.tab-btn.active {
    color: var(--text-main);
    border-bottom-color: var(--text-main);
}

/* Action Buttons */
.btn-text {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

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

.btn-play {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border);
    background: transparent;
    color: var(--text-main);
    font-family: var(--font-main);
    font-size: 0.9rem;
    cursor: pointer;
    border-radius: 6px;
    font-weight: 600;
    transition: 0.2s;
}

.btn-play:hover {
    background: rgba(255, 255, 255, 0.05);
    border-color: var(--text-main);
}

.btn-play.primary {
    background: var(--text-main);
    color: #000;
    border: none;
}

.btn-play.primary:hover {
    opacity: 0.9;
    transform: translateY(-1px);
}

/* --- Responsive --- */
@media (max-width: 900px) {
    .transposer-engine {
        grid-template-columns: 1fr;
        max-width: 600px;
        margin: 0 auto;
    }

    .io-card {
        height: 350px;
    }

    .engine-controls {
        flex-direction: row;
        flex-wrap: wrap;
        justify-content: center;
    }

    .control-group {
        width: 45%;
        min-width: 150px;
    }
}