:root {
    color-scheme: light dark;

    --bg: #f4f4f4;
    --card-bg: #ffffff;
    --text: #222;
    --text-muted: #555;
    --text-faint: #999;

    --border: #eee;
    --border-strong: #ddd;
    --border-input: #ccc;
    --border-hover: #aaa;

    --accent: #4caf50;
    --accent-hover: #43a047;
    --accent-soft: rgba(76, 175, 80, 0.08);
    --accent-soft-strong: rgba(76, 175, 80, 0.15);

    --danger: #e74c3c;
    --danger-bg: #fdecea;
    --correct: green;
    --wrong: red;

    --dock-bg: rgba(255, 255, 255, 0.8);
    --dock-border: rgba(0, 0, 0, 0.08);
    --dock-shadow: rgba(16, 22, 30, 0.18);

    --progress-bg: #ddd;
    --big-score-outline: #fff;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg: #121417;
        --card-bg: #1c1f23;
        --text: #e8e8ea;
        --text-muted: #aeb2b6;
        --text-faint: #888c90;

        --border: #2c2f33;
        --border-strong: #3a3d41;
        --border-input: #45484c;
        --border-hover: #5a5d61;

        --accent: #4caf50;
        --accent-hover: #5cbf60;
        --accent-soft: rgba(76, 175, 80, 0.16);
        --accent-soft-strong: rgba(76, 175, 80, 0.25);

        --danger: #ff6b5b;
        --danger-bg: #3a1f1c;
        --correct: #66bb6a;
        --wrong: #ff5252;

        --dock-bg: rgba(28, 31, 35, 0.8);
        --dock-border: rgba(255, 255, 255, 0.08);
        --dock-shadow: rgba(0, 0, 0, 0.5);

        --progress-bg: #2c2f33;
        --big-score-outline: #1c1f23;
    }
}

* {
    box-sizing: border-box;
}

body {
    font-family: "SF Pro Display", "SF Pro Text", "SF Pro", "Helvetica Neue", sans-serif;
    margin: 0;
    background: var(--bg);
    color: var(--text);
    text-align: center;
    transition: background 0.2s ease, color 0.2s ease;
}

#start-screen,
#quiz-screen,
#results-screen {
    max-width: 500px;
    margin: auto;
    padding: 20px;
}

#start-screen {
    padding-bottom: calc(120px + env(safe-area-inset-bottom));
}

button {
    padding: 12px 25px;
    margin-top: 15px;
    cursor: pointer;
    font-size: 18px;
    font-family: inherit;
}

.btn-primary,
.btn-secondary {
    display: flex;
    align-items: center;
    justify-content: center;
    flex: 1;
    width: 100%;
    border-radius: 999px;
    font-weight: 600;
    white-space: nowrap;
    transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.btn-primary {
    background: var(--accent);
    border: 2px solid var(--accent);
    color: #fff;
    font-size: 17px;
}

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

.btn-secondary {
    background: var(--card-bg);
    border: 1.5px solid var(--accent);
    color: var(--accent);
    font-size: 15px;
}

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

input, select {
    padding: 10px;
    font-size: 16px;
    width: 80%;
    margin-bottom: 15px;
    background: var(--card-bg);
    color: var(--text);
    border: 1px solid var(--border-input);
    border-radius: 12px;
}

.field {
    text-align: left;
    margin-bottom: 15px;
}

.field label {
    display: block;
    font-size: 14px;
    font-weight: bold;
    color: var(--text-muted);
    margin-bottom: 6px;
}

.field input[type="number"] {
    width: 100%;
    margin-bottom: 0;
}

#answer::-webkit-outer-spin-button,
#answer::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

#answer {
    -moz-appearance: textfield;
}

.field-row {
    display: flex;
    gap: 15px;
    margin-bottom: 15px;
}

.field-row .field {
    flex: 1;
    margin-bottom: 0;
}

.dock-nav {
    position: fixed;
    left: 16px;
    right: 16px;
    bottom: calc(16px + env(safe-area-inset-bottom));
    max-width: 468px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
    padding: 10px;
    background: var(--dock-bg);
    border-radius: 12px;
    border: 1px solid var(--dock-border);
    -webkit-backdrop-filter: saturate(1.8) blur(20px);
    backdrop-filter: saturate(1.8) blur(20px);
    box-shadow: 0 12px 30px var(--dock-shadow);
    z-index: 5;
}

.tab-btn {
    margin-top: 0;
    font-family: inherit;
    font-size: 13px;
    font-weight: 600;
    border: none;
    background: transparent;
    color: var(--text-faint);
    cursor: pointer;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 6px;
    padding: 10px 4px;
    border-radius: 12px;
    transition: background 0.2s ease, color 0.2s ease;
}

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

.tab-btn.active {
    background: var(--accent-soft-strong);
    color: var(--accent);
}

.tab-icon {
    width: 22px;
    height: 22px;
    display: grid;
    place-items: center;
}

.btn-group {
    display: flex;
    gap: 8px;
}

.option-btn {
    flex: 1;
    padding: 10px 4px;
    margin-top: 0;
    font-size: 14px;
    font-family: inherit;
    font-weight: 600;
    border: 1.5px solid var(--border-input);
    background: var(--card-bg);
    color: var(--text-faint);
    border-radius: 999px;
    cursor: pointer;
    transition: border-color 0.15s ease, background 0.15s ease, color 0.15s ease;
}

.option-btn:hover {
    border-color: var(--border-hover);
    color: var(--text-muted);
}

.option-btn.active {
    background: var(--card-bg);
    border-color: var(--accent);
    color: var(--accent);
}

#progress-bar {
    height: 20px;
    width: 100%;
    background: var(--progress-bg);
    border-radius: 12px;
    overflow: hidden;
    margin: 10px 0;
}

#progress-bar-fill {
    height: 100%;
    width: 100%;
    background: var(--accent);
    transition: width 1s linear;
}

#control-bar {
    display: flex;
    justify-content: space-between;
    margin-top: 20px;
}

#question-stats {
    text-align: left;
    max-height: 300px;
    overflow-y: auto;
    padding: 10px;
    background: var(--card-bg);
    border-radius: 12px;
}

.correct {
    color: var(--correct);
}

.wrong {
    color: var(--wrong);
    text-decoration: line-through;
}

#big-score {
    font-size: 64px;
    font-weight: 900;
    color: #ff4081;
    font-family: "Comic Sans MS", "Fredoka One", "Baloo", cursive;
    margin: 0;
    text-shadow: 3px 3px 0 var(--big-score-outline), 6px 6px 0 #f48fb1;
}

#history-chart-section {
    margin-top: 25px;
}

#history-chart {
    max-width: 100%;
    height: auto;
    background: var(--card-bg);
    border-radius: 12px;
}

#marathon-chart-section {
    margin-top: 25px;
}

#marathon-chart {
    max-width: 100%;
    height: auto;
    background: var(--card-bg);
    border-radius: 12px;
}

#attempts-history-section {
    margin-top: 25px;
}

#attempts-table-wrap {
    max-width: 500px;
    max-height: 320px;
    margin: 0 auto;
    overflow-y: auto;
    background: var(--card-bg);
    border-radius: 12px;
    padding: 4px 10px;
    text-align: left;
}

#attempts-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 13px;
}

#attempts-table th,
#attempts-table td {
    padding: 6px 8px;
    text-align: left;
    border-bottom: 1px solid var(--border);
    white-space: nowrap;
}

#attempts-table th {
    color: var(--text-muted);
    position: sticky;
    top: 0;
    background: var(--card-bg);
}

#attempts-table tbody tr:last-child td {
    border-bottom: none;
}

#score-fraction {
    font-size: 20px;
    font-weight: bold;
    color: var(--text-muted);
    margin: 0 0 10px;
}

#start-actions {
    display: flex;
    justify-content: center;
    gap: 15px;
}

#results-actions {
    display: flex;
    justify-content: center;
    gap: 15px;
}

.gen-set {
    padding: 15px;
    margin-bottom: 20px;
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 12px;
}

.gen-set-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 12px;
}

.gen-set-label {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--accent);
    color: #fff;
    font-weight: bold;
    flex-shrink: 0;
}

.gen-set-header input[type="number"] {
    width: 90px;
    margin-bottom: 0;
}

.gen-count-label {
    color: var(--text-muted);
    font-size: 15px;
}

.gen-remove-set-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 0 0 auto;
    padding: 0;
    width: 28px;
    height: 28px;
    border: none;
    border-radius: 50%;
    background: var(--bg);
    color: var(--text-faint);
    cursor: pointer;
    flex-shrink: 0;
}

.gen-remove-set-btn:hover {
    background: #e74c3c;
    color: #fff;
}

.gen-formula {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    align-items: center;
    min-height: 44px;
    padding: 10px;
    margin-bottom: 15px;
    background: var(--card-bg);
    border: 2px dashed var(--border-strong);
    border-radius: 12px;
    text-align: left;
}

.gen-formula-empty {
    color: var(--text-faint);
    font-size: 14px;
}

.gen-chip {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 6px 10px;
    background: var(--accent);
    color: #fff;
    border-radius: 12px;
    font-size: 13px;
    font-weight: bold;
}

.gen-chip-remove {
    padding: 0;
    margin: 0;
    width: 18px;
    height: 18px;
    line-height: 1;
    border: none;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.3);
    color: #fff;
    font-size: 13px;
    cursor: pointer;
}

.gen-formula-actions {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    margin-bottom: 0;
}

.gen-formula-actions button {
    padding: 6px 14px;
    margin-top: 0;
    font-size: 13px;
}

#gen-actions,
#gen-check-actions {
    display: flex;
    justify-content: center;
    gap: 15px;
}

#gen-error {
    color: var(--danger);
    background: var(--danger-bg);
    border-radius: 12px;
    padding: 10px;
    margin-top: 15px;
    font-size: 14px;
    text-align: left;
}

#gen-questions {
    text-align: left;
    padding: 10px;
    background: var(--card-bg);
    border-radius: 12px;
    margin-top: 15px;
}

.gen-set-divider {
    margin: 14px -10px 4px;
    padding: 6px 14px;
    background: var(--bg);
    color: var(--text-muted);
    font-weight: bold;
    font-size: 13px;
}

.gen-set-divider:first-child {
    margin-top: -10px;
    border-radius: 12px 12px 0 0;
}

.gen-question {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 4px;
    border-bottom: 1px solid var(--border);
}

.gen-question:last-child {
    border-bottom: none;
}

.gen-question-text {
    flex: 1;
    font-size: 16px;
    font-weight: bold;
}

.gen-answer-input {
    width: 90px;
    flex-shrink: 0;
    margin-bottom: 0;
    padding: 6px;
    font-size: 15px;
}

.gen-result-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 26px;
    height: 26px;
    flex-shrink: 0;
    border-radius: 50%;
    visibility: hidden;
}

.gen-result-badge.correct {
    background: green;
    visibility: visible;
}

.gen-result-badge.wrong {
    background: red;
    visibility: visible;
}

#gen-score {
    margin-top: 15px;
    font-size: 22px;
    font-weight: bold;
    color: var(--accent);
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.info-block {
    text-align: left;
    padding: 15px;
    margin-bottom: 15px;
    background: var(--card-bg);
    border-radius: 12px;
}

.info-block h3 {
    margin-top: 0;
}

.info-block p {
    color: var(--text);
    line-height: 1.5;
}

.info-block p:last-child {
    margin-bottom: 0;
}

.info-modes {
    margin: 0;
}

.info-modes dt {
    font-weight: bold;
    color: var(--accent);
    margin-top: 12px;
}

.info-modes dt:first-child {
    margin-top: 0;
}

.info-modes dd {
    margin: 4px 0 0;
    color: var(--text);
    line-height: 1.5;
}

.info-install-list {
    margin: 0 0 10px;
    padding-left: 20px;
    color: var(--text);
    line-height: 1.6;
}

.info-note {
    font-size: 13px;
    color: var(--text-faint);
}

.install-banner {
    position: fixed;
    left: 12px;
    right: 12px;
    bottom: calc(108px + env(safe-area-inset-bottom));
    max-width: 460px;
    margin: 0 auto;
    background: linear-gradient(160deg, #1b5e20, #2e7d32);
    color: #fff;
    border-radius: 12px;
    padding: 16px 44px 18px 16px;
    box-shadow: 0 16px 40px rgba(0, 0, 0, 0.35);
    z-index: 20;
    text-align: left;
    animation: install-banner-in 0.3s ease;
}

@keyframes install-banner-in {
    from { transform: translateY(16px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}

.install-banner-close {
    position: absolute;
    top: 12px;
    right: 12px;
    width: 26px;
    height: 26px;
    border: none;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.18);
    color: #fff;
    font-size: 16px;
    line-height: 1;
    padding: 0;
    margin: 0;
    cursor: pointer;
    display: grid;
    place-items: center;
}

.install-banner-close:hover {
    background: rgba(255, 255, 255, 0.3);
}

.install-banner-top {
    display: flex;
    gap: 12px;
    align-items: flex-start;
}

.install-banner-icon {
    width: 52px;
    height: 52px;
    border-radius: 12px;
    flex-shrink: 0;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.25);
}

.install-banner-title {
    margin: 0 0 4px;
    font-size: 17px;
    font-weight: 700;
}

.install-banner-text {
    margin: 0;
    font-size: 13.5px;
    line-height: 1.4;
    color: rgba(255, 255, 255, 0.85);
}

.install-banner-steps {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-top: 12px;
    padding-left: 64px;
}

.install-banner-step {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 14px;
    font-weight: 600;
}

.install-banner-step-icon {
    width: 24px;
    height: 24px;
    display: grid;
    place-items: center;
    flex-shrink: 0;
}

.install-banner-action {
    margin: 14px 0 0;
    width: 100%;
    background: #fff;
    border-color: #fff;
    color: #1b5e20;
    font-size: 15px;
    padding: 10px 20px;
}

.install-banner-action:hover {
    background: #f1f8f1;
    border-color: #f1f8f1;
}

#fireworks-canvas {
    position: absolute;
    top: 0; left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none; /* allow clicking buttons */
    display: none; /* only shown on perfect score */
}