/* === tokens === */
:root {
    --ff-display: 'Fraunces', Georgia, serif;
    --ff-body: 'DM Sans', system-ui, sans-serif;
    --clr-bg: #faf8f4;
    --clr-surface: #ffffff;
    --clr-surface-raised: #fff;
    --clr-ink: #2a2520;
    --clr-ink-dim: #8a8078;
    --clr-ink-faint: #c4bdb6;
    --clr-border: #e8e2da;
    --clr-accent: #d16b3f;
    --clr-accent-soft: #fdf0ea;
    --clr-header: #2a2520;
    --clr-g1: #4caf7d;
    --clr-g2: #4a90c4;
    --clr-g3: #d4943a;
    --clr-g4: #c45454;
    --radius: 10px;
    --shadow-sm: 0 1px 2px rgba(42,37,32,.06);
    --shadow-md: 0 4px 12px rgba(42,37,32,.07);
    --transition: 180ms ease;
}

/* === reset === */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
body {
    font-family: var(--ff-body);
    background: var(--clr-bg);
    color: var(--clr-ink);
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
}

/* subtle paper texture */
body::before {
    content: '';
    position: fixed;
    inset: 0;
    pointer-events: none;
    opacity: .35;
    background-image: url("data:image/svg+xml,%3Csvg width='40' height='40' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence baseFrequency='.85' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)' opacity='.04'/%3E%3C/svg%3E");
    z-index: 9999;
}

/* === header === */
header {
    background: var(--clr-header);
    color: #f5f0eb;
    padding: 0 28px;
    position: sticky;
    top: 0;
    z-index: 100;
}
.header-inner {
    max-width: 1180px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 62px;
}
.logo-group {
    display: flex;
    align-items: center;
    gap: 14px;
}
.logo-mark {
    display: grid;
    grid-template-columns: 10px 10px;
    gap: 3px;
}
.dot { display: block; width: 10px; height: 10px; border-radius: 3px; }
.d1 { background: var(--clr-g1); }
.d2 { background: var(--clr-g2); }
.d3 { background: var(--clr-g3); }
.d4 { background: var(--clr-g4); }
header h1 {
    font-family: var(--ff-display);
    font-weight: 500;
    font-size: 18px;
    letter-spacing: -.01em;
    line-height: 1.1;
}
.header-tagline {
    font-size: 11.5px;
    opacity: .55;
    margin-top: 1px;
}

/* lang pill */
.lang-pill {
    display: flex;
    align-items: center;
    gap: 5px;
    background: rgba(255,255,255,.1);
    border-radius: 20px;
    padding: 5px 10px 5px 10px;
}
.lang-pill svg { opacity: .6; flex-shrink: 0; }
.lang-pill select {
    appearance: none;
    background: none;
    border: none;
    color: inherit;
    font: inherit;
    font-size: 12.5px;
    cursor: pointer;
    padding-right: 2px;
}
.lang-pill select option { color: var(--clr-ink); }

/* === grade bar (top nav) === */
#grade-bar {
    background: var(--clr-surface);
    border-bottom: 1px solid var(--clr-border);
    position: sticky;
    top: 62px;
    z-index: 99;
}
.grade-bar-inner {
    max-width: 1180px;
    margin: 0 auto;
    padding: 0 28px;
}

/* === layout === */
main {
    display: flex;
    max-width: 1180px;
    margin: 0 auto;
    gap: 24px;
    padding: 24px 28px 48px;
    align-items: flex-start;
}

/* === sidebar === */
#exercise-picker {
    width: 264px;
    flex-shrink: 0;
    position: sticky;
    top: 110px;
    background: var(--clr-surface);
    border-radius: var(--radius);
    border: 1px solid var(--clr-border);
    overflow: hidden;
}
.picker-head {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    padding: 16px 16px 12px;
    border-bottom: 1px solid var(--clr-border);
}
.picker-head h2 {
    font-family: var(--ff-display);
    font-weight: 600;
    font-size: 15px;
}
.picker-hint {
    font-size: 11px;
    color: var(--clr-ink-dim);
    font-style: italic;
}

/* grade tabs (in top bar) */
#grade-tabs {
    display: flex;
    gap: 0;
}
.grade-tab {
    padding: 10px 24px;
    border: none;
    background: transparent;
    font-family: var(--ff-body);
    font-size: 13px;
    font-weight: 500;
    cursor: pointer;
    color: var(--clr-ink-dim);
    transition: all var(--transition);
    position: relative;
    border-bottom: 2.5px solid transparent;
}
.grade-tab:hover { color: var(--clr-ink); background: var(--clr-bg); }
.grade-tab.active { color: var(--clr-ink); font-weight: 600; }
.grade-tab[data-grade="1"].active { border-bottom-color: var(--clr-g1); color: var(--clr-g1); }
.grade-tab[data-grade="2"].active { border-bottom-color: var(--clr-g2); color: var(--clr-g2); }
.grade-tab[data-grade="3"].active { border-bottom-color: var(--clr-g3); color: var(--clr-g3); }
.grade-tab[data-grade="4"].active { border-bottom-color: var(--clr-g4); color: var(--clr-g4); }

/* exercise cards */
#exercise-list { padding: 10px 10px 12px; }
.exercise-item {
    padding: 10px 12px;
    border-radius: 8px;
    cursor: pointer;
    transition: all var(--transition);
    border: 1px solid transparent;
    margin-bottom: 2px;
}
.exercise-item:hover {
    background: var(--clr-accent-soft);
    border-color: rgba(209,107,63,.15);
}
.exercise-item:active { transform: scale(.98); }
.exercise-item .name {
    font-weight: 600;
    font-size: 13px;
    line-height: 1.3;
}
.exercise-item .desc {
    font-size: 11.5px;
    color: var(--clr-ink-dim);
    margin-top: 1px;
}

/* exercise hints */
.exercise-hint {
    font-family: 'DM Mono', 'SF Mono', 'Menlo', monospace;
    font-size: 11px;
    color: var(--clr-ink-dim);
    background: var(--clr-bg);
    border-radius: 4px;
    padding: 4px 8px;
    margin-top: 5px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    letter-spacing: .02em;
}
.block-hint {
    margin-top: 8px;
}

/* === worksheet area === */
#worksheet-area { flex: 1; min-width: 0; }

/* settings bar */
#settings-bar {
    display: flex;
    align-items: flex-end;
    gap: 16px;
    margin-bottom: 16px;
    padding: 14px 18px;
    background: var(--clr-surface);
    border: 1px solid var(--clr-border);
    border-radius: var(--radius);
}
.field { display: flex; flex-direction: column; gap: 4px; flex: 1; }
.field.narrow { flex: 0 0 72px; }
.field-label {
    font-size: 11px;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: .05em;
    color: var(--clr-ink-dim);
    white-space: nowrap;
}
.field input[type="text"],
.field input[type="number"] {
    font-family: var(--ff-body);
    font-size: 14px;
    padding: 6px 10px;
    border: 1px solid var(--clr-border);
    border-radius: 6px;
    background: var(--clr-bg);
    color: var(--clr-ink);
    transition: border var(--transition);
    width: 100%;
}
.field input:focus {
    outline: none;
    border-color: var(--clr-accent);
    box-shadow: 0 0 0 3px rgba(209,107,63,.1);
}

/* block list */
#block-list { min-height: 160px; }

/* empty state */
#empty-msg {
    text-align: center;
    padding: 56px 24px;
    border: 1.5px dashed var(--clr-border);
    border-radius: var(--radius);
    background: var(--clr-surface);
}
.empty-icon { color: var(--clr-ink-faint); margin-bottom: 12px; }
.empty-title {
    font-family: var(--ff-display);
    font-weight: 500;
    font-size: 16px;
    margin-bottom: 4px;
}
.empty-sub { font-size: 13px; color: var(--clr-ink-dim); }

/* === exercise blocks === */
.block {
    background: var(--clr-surface);
    border: 1px solid var(--clr-border);
    border-radius: var(--radius);
    padding: 14px 16px;
    margin-bottom: 8px;
    border-left: 4px solid var(--clr-ink-faint);
    transition: box-shadow var(--transition), border-color var(--transition);
    animation: slideIn 220ms ease-out;
}
@keyframes slideIn {
    from { opacity: 0; transform: translateY(-6px); }
    to   { opacity: 1; transform: translateY(0); }
}
.block:hover { box-shadow: var(--shadow-md); }
.block.grade-1 { border-left-color: var(--clr-g1); }
.block.grade-2 { border-left-color: var(--clr-g2); }
.block.grade-3 { border-left-color: var(--clr-g3); }
.block.grade-4 { border-left-color: var(--clr-g4); }

.block-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
}
.block-info {
    cursor: pointer;
    display: flex;
    align-items: center;
    padding: 2px 0;
    border-radius: 4px;
}
.block-info:hover .block-title { color: var(--clr-accent); }
.block-num {
    font-size: 12px;
    font-weight: 600;
    color: var(--clr-ink-faint);
    margin-right: 8px;
    min-width: 16px;
}
.block-title {
    font-family: var(--ff-display);
    font-weight: 600;
    font-size: 14px;
    transition: color var(--transition);
}
.block-grade {
    font-size: 11px;
    color: var(--clr-ink-dim);
    margin-left: 8px;
    font-weight: 500;
}
.block-chevron {
    margin-left: 6px;
    font-size: 11px;
    color: var(--clr-ink-faint);
    transition: color var(--transition);
}
.block-info:hover .block-chevron { color: var(--clr-accent); }

.block-controls { display: flex; gap: 4px; align-items: center; }
.block-controls button,
.block-controls .drag-handle {
    width: 30px;
    height: 30px;
    display: grid;
    place-items: center;
    background: none;
    border: 1px solid transparent;
    border-radius: 6px;
    cursor: pointer;
    font-size: 18px;
    color: var(--clr-ink-dim);
    transition: all var(--transition);
    line-height: 1;
}
.block-controls .drag-handle {
    cursor: grab;
    color: var(--clr-ink-faint);
}
.block-controls .drag-handle:hover { color: var(--clr-ink-dim); }
.block-controls button:hover {
    background: var(--clr-bg);
    border-color: var(--clr-border);
    color: var(--clr-ink);
}
.block.dragging { opacity: 0.4; }
.block.drag-over { border-top: 3px solid var(--clr-accent); }
.block-controls button:disabled {
    opacity: .25;
    cursor: default;
    background: none;
    border-color: transparent;
}
.block-controls .remove-btn:hover {
    background: #fdf0ee;
    border-color: #e8b4aa;
    color: var(--clr-g4);
}

/* config panel */
.block-config {
    max-height: 0;
    overflow: hidden;
    transition: max-height 250ms ease, margin 250ms ease, padding 250ms ease;
    margin-top: 0;
    padding-top: 0;
}
.block-config.open {
    max-height: 500px;
    margin-top: 12px;
    padding-top: 12px;
    border-top: 1px solid var(--clr-border);
}
.config-field {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 8px;
}
.config-field label:first-child {
    font-size: 12.5px;
    width: 155px;
    flex-shrink: 0;
    color: var(--clr-ink-dim);
}
.config-field input,
.config-field select {
    font-family: var(--ff-body);
    font-size: 13px;
    padding: 5px 8px;
    border: 1px solid var(--clr-border);
    border-radius: 6px;
    background: var(--clr-bg);
    color: var(--clr-ink);
    transition: border var(--transition);
}
.config-field input:focus,
.config-field select:focus {
    outline: none;
    border-color: var(--clr-accent);
}
.config-field input[type="number"] { width: 68px; }
.config-field input[type="checkbox"] { width: 15px; height: 15px; accent-color: var(--clr-accent); }
.multi-check {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}
.multi-check label {
    width: auto !important;
    display: flex;
    align-items: center;
    gap: 4px;
    font-size: 12px !important;
    color: var(--clr-ink) !important;
}

/* === generate button === */
#generate-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    width: 100%;
    padding: 15px;
    margin-top: 16px;
    background: var(--clr-accent);
    color: #fff;
    font-family: var(--ff-body);
    font-size: 15px;
    font-weight: 600;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    transition: all var(--transition);
    box-shadow: 0 2px 8px rgba(209,107,63,.25);
}
#generate-btn:hover:not(:disabled) {
    background: #b85a33;
    box-shadow: 0 4px 16px rgba(209,107,63,.3);
    transform: translateY(-1px);
}
#generate-btn:active:not(:disabled) { transform: translateY(0); }
#generate-btn:disabled {
    background: var(--clr-ink-faint);
    box-shadow: none;
    cursor: not-allowed;
}
.btn-icon { flex-shrink: 0; }

/* === responsive === */
@media (max-width: 768px) {
    main { flex-direction: column; padding: 16px; }
    #exercise-picker { width: 100%; position: static; }
    .header-inner { height: 56px; }
}