:root {
    --primary: #6366f1;
    --primary-light: #818cf8;
    --primary-dark: #4f46e5;
    --success: #10b981;
    --error: #ef4444;
    --background: #f9fafb;
    --card: #ffffff;
    --text: #1f2937;
    --text-light: #6b7280;
    --border: #e5e7eb;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --background-dark: #1f2937;
    --card-dark: #374151;
    --text-dark: #f3f4f6;
    --text-light-dark: #9ca3af;
    --border-dark: #4b5563;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--background);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    transition: background-color 0.3s ease, color 0.3s ease;
    overflow-x: hidden;
    position: relative;
}

body.dark {
    background-color: var(--background-dark);
    color: var(--text-dark);
}

/* Animated Background */
.animated-background {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    overflow: hidden;
}

.shape {
    position: absolute;
    border-radius: 50%;
    opacity: 0.1;
    filter: blur(60px);
    animation: float 20s infinite ease-in-out;
}

.shape-1 {
    width: 400px;
    height: 400px;
    background-color: var(--primary);
    top: -100px;
    left: -100px;
    animation-delay: 0s;
}

.shape-2 {
    width: 300px;
    height: 300px;
    background-color: var(--success);
    bottom: -50px;
    right: -50px;
    animation-delay: -5s;
}

.shape-3 {
    width: 200px;
    height: 200px;
    background-color: var(--primary-light);
    bottom: 30%;
    left: 10%;
    animation-delay: -10s;
}

.shape-4 {
    width: 250px;
    height: 250px;
    background-color: var(--error);
    top: 20%;
    right: 10%;
    animation-delay: -15s;
}

@keyframes float {
    0% {
        transform: translate(0, 0) rotate(0deg);
    }

    25% {
        transform: translate(5%, 5%) rotate(5deg);
    }

    50% {
        transform: translate(0, 10%) rotate(0deg);
    }

    75% {
        transform: translate(-5%, 5%) rotate(-5deg);
    }

    100% {
        transform: translate(0, 0) rotate(0deg);
    }
}

.quiz-background .shape {
    opacity: 0.05;
}

/* Container Styles */
.container {
    width: 100%;
    max-width: 600px;
    background-color: var(--card);
    border-radius: 1rem;
    box-shadow: var(--shadow);
    padding: 2rem;
    transition: all 0.3s ease;
    position: relative;
    z-index: 1;
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    background-color: rgba(255, 255, 255, 0.9);
}

body.dark .container {
    background-color: rgba(55, 65, 81, 0.9);
    color: var(--text-dark);
}

/* Home Page Styles */
.home-container {
    max-width: 700px;
}

.home-title {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 0.5rem;
    color: var(--primary-dark);
    text-align: center;
    transition: color 0.3s ease;
    letter-spacing: -0.5px;
}

body.dark .home-title {
    color: var(--primary-light);
}

.home-subtitle {
    text-align: center;
    font-size: 1.2rem;
    color: var(--text-light);
    margin-bottom: 2.5rem;
}

body.dark .home-subtitle {
    color: var(--text-light-dark);
}

.settings-section {
    margin-bottom: 2.5rem;
}

.settings-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    color: var(--text);
    text-align: center;
}

body.dark .settings-title {
    color: var(--text-dark);
}

.settings-group {
    margin-bottom: 2rem;
    padding: 1.5rem;
    background-color: rgba(255, 255, 255, 0.5);
    border-radius: 0.75rem;
    transition: background-color 0.3s ease;
}

body.dark .settings-group {
    background-color: rgba(55, 65, 81, 0.5);
}

.settings-subtitle {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text);
}

body.dark .settings-subtitle {
    color: var(--text-dark);
}

.operations-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
}

.operation-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.75rem;
    border-radius: 0.5rem;
    background-color: var(--card);
    transition: background-color 0.2s ease, transform 0.2s ease;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

.operation-item:hover {
    transform: translateY(-2px);
}

body.dark .operation-item {
    background-color: var(--card-dark);
}

.operation-label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 500;
}

.operation-symbol {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--primary);
    min-width: 1.5rem;
    text-align: center;
}

body.dark .operation-symbol {
    color: var(--primary-light);
}

.operation-toggle-track {
    position: relative;
    display: inline-block;
    width: 2.5rem;
    height: 1.25rem;
    border-radius: 1.25rem;
    background-color: var(--border);
    transition: 0.3s;
    cursor: pointer;
}

.operation-toggle-track.active {
    background-color: var(--primary);
}

.operation-toggle-thumb {
    position: absolute;
    top: 0.125rem;
    left: 0.125rem;
    width: 1rem;
    height: 1rem;
    border-radius: 50%;
    background-color: white;
    transition: 0.3s;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
}

.operation-toggle-track.active .operation-toggle-thumb {
    left: calc(100% - 1.125rem);
}

.operation-toggle input {
    opacity: 0;
    width: 0;
    height: 0;
    position: absolute;
}

/* Difficulty Selector */
.difficulty-selector {
    display: flex;
    gap: 0.5rem;
    justify-content: center;
}

.difficulty-btn {
    padding: 0.75rem 1.25rem;
    border-radius: 0.5rem;
    border: 2px solid var(--border);
    background-color: var(--card);
    color: var(--text);
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.difficulty-btn:hover {
    border-color: var(--primary-light);
}

.difficulty-btn.active {
    background-color: var(--primary);
    border-color: var(--primary);
    color: white;
}

body.dark .difficulty-btn {
    background-color: var(--card-dark);
    border-color: var(--border-dark);
    color: var(--text-dark);
}

body.dark .difficulty-btn:hover {
    border-color: var(--primary-light);
}

body.dark .difficulty-btn.active {
    background-color: var(--primary);
    border-color: var(--primary);
    color: white;
}

/* Time Selector */
.time-selector {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    justify-content: center;
}

.time-btn {
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    border: 2px solid var(--border);
    background-color: var(--card);
    color: var(--text);
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
}

.time-btn:hover {
    border-color: var(--primary-light);
}

.time-btn.active {
    background-color: var(--primary);
    border-color: var(--primary);
    color: white;
}

body.dark .time-btn {
    background-color: var(--card-dark);
    border-color: var(--border-dark);
    color: var(--text-dark);
}

body.dark .time-btn:hover {
    border-color: var(--primary-light);
}

body.dark .time-btn.active {
    background-color: var(--primary);
    border-color: var(--primary);
    color: white;
}

/* Start Section */
.start-section {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

.start-btn {
    background-color: var(--primary);
    color: white;
    border: none;
    border-radius: 0.75rem;
    padding: 1rem 2.5rem;
    font-size: 1.25rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: 0 4px 6px -1px rgba(99, 102, 241, 0.4);
}

.start-btn:hover {
    background-color: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 6px 10px -1px rgba(99, 102, 241, 0.5);
}

.start-btn:active {
    transform: translateY(0);
    box-shadow: 0 2px 4px -1px rgba(99, 102, 241, 0.4);
}

.start-hint {
    color: var(--text-light);
    font-size: 0.9rem;
}

body.dark .start-hint {
    color: var(--text-light-dark);
}

.key-hint {
    background-color: var(--border);
    padding: 0.1rem 0.4rem;
    border-radius: 0.25rem;
    font-family: monospace;
    font-weight: 600;
}

body.dark .key-hint {
    background-color: var(--border-dark);
}

/* Quiz Page Styles */
.quiz-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.back-btn {
    background: none;
    border: none;
    color: var(--text-light);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: color 0.2s ease;
    display: flex;
    align-items: center;
    padding: 0.5rem;
}

.back-btn:hover {
    color: var(--primary);
}

body.dark .back-btn {
    color: var(--text-light-dark);
}

body.dark .back-btn:hover {
    color: var(--primary-light);
}

.timer-container {
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 1rem;
}

.timer-container.hidden {
    display: none;
}

.timer-bar {
    flex: 1;
    height: 0.5rem;
    background-color: var(--border);
    border-radius: 0.25rem;
    overflow: hidden;
}

.timer-progress {
    height: 100%;
    background-color: var(--primary);
    width: 100%;
    transition: width 1s linear;
}

.timer-text {
    font-weight: 600;
    min-width: 3rem;
    text-align: right;
}

.title {
    font-size: 1.8rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    color: var(--primary-dark);
    text-align: center;
    transition: color 0.3s ease;
}

body.dark .title {
    color: var(--primary-light);
}

.problem {
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 2rem;
    font-size: 2.5rem;
    font-weight: 600;
}

.problem span {
    display: inline-block;
    min-width: 3rem;
    text-align: center;
}

.equals {
    margin: 0 1rem;
}

.input-group {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 2rem;
}

input[type="text"] {
    flex: 1;
    padding: 0.75rem 1rem;
    font-size: 1.25rem;
    border: 2px solid var(--border);
    border-radius: 0.5rem;
    outline: none;
    transition: border-color 0.2s ease, background-color 0.3s ease, color 0.3s ease;
    text-align: center;
    background-color: var(--card);
    color: var(--text);
}

input[type="text"]:focus {
    border-color: var(--primary);
}

body.dark input[type="text"] {
    background-color: var(--background-dark);
    color: var(--text-dark);
    border-color: var(--border-dark);
}

button {
    background-color: var(--primary);
    color: white;
    border: none;
    border-radius: 0.5rem;
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.2s ease, transform 0.1s ease;
    outline: none;
}

button:hover {
    background-color: var(--primary-dark);
}

button:active {
    transform: translateY(2px);
}

.new-problem-btn {
    background-color: transparent;
    color: var(--primary);
    border: 2px solid var(--primary);
    margin-top: 1rem;
    width: 100%;
    transition: background-color 0.2s ease, color 0.3s ease, border-color 0.3s ease;
}

.new-problem-btn:hover {
    background-color: var(--primary-light);
    color: white;
}

body.dark .new-problem-btn {
    color: var(--primary-light);
    border-color: var(--primary-light);
}

#feedbackDiv {
    min-height: 5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    font-weight: 500;
    border-radius: 0.5rem;
    padding: 1rem;
    margin-bottom: 1rem;
    transition: all 0.3s ease;
}

.feedback-success {
    background-color: rgba(16, 185, 129, 0.1);
    color: var(--success);
    border-left: 4px solid var(--success);
}

.feedback-error {
    background-color: rgba(239, 68, 68, 0.1);
    color: var(--error);
    border-left: 4px solid var(--error);
}

.feedback-neutral {
    background-color: transparent;
}

body.dark .feedback-success {
    background-color: rgba(16, 185, 129, 0.2);
}

body.dark .feedback-error {
    background-color: rgba(239, 68, 68, 0.2);
}

.stats-container {
    display: flex;
    justify-content: space-between;
    margin-top: 1.5rem;
}

.score,
.streak {
    text-align: center;
    font-size: 1rem;
    color: var(--text-light);
    transition: color 0.3s ease;
}

body.dark .score,
body.dark .streak {
    color: var(--text-light-dark);
}

.score-value,
.streak-value {
    font-weight: 700;
    color: var(--primary);
}

@keyframes pulse {
    0% {
        transform: scale(1);
    }

    50% {
        transform: scale(1.05);
    }

    100% {
        transform: scale(1);
    }
}

.pulse {
    animation: pulse 0.5s ease-in-out;
}

/* Theme Toggle Styles */
.theme-toggle {
    display: flex;
    align-items: center;
    z-index: 10;
}

.theme-toggle-track {
    position: relative;
    display: inline-block;
    width: 3.5rem;
    height: 1.75rem;
    border-radius: 1.75rem;
    background-color: #cbd5e1;
    transition: 0.3s;
    cursor: pointer;
    box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1);
}

body.dark .theme-toggle-track {
    background-color: #475569;
}

.theme-toggle-thumb {
    position: absolute;
    top: 0.2rem;
    left: 0.2rem;
    width: 1.35rem;
    height: 1.35rem;
    border-radius: 50%;
    background-color: white;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.2);
    transition: 0.3s;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fbbf24;
}

body.dark .theme-toggle-thumb {
    left: calc(100% - 1.55rem);
    background-color: #1f2937;
    color: #f3f4f6;
}

.theme-toggle input {
    opacity: 0;
    width: 0;
    height: 0;
    position: absolute;
}

.theme-toggle-icon {
    font-size: 0.8rem;
    line-height: 1;
}

/* Responsive Styles */
@media (max-width: 640px) {
    .container {
        padding: 1.5rem;
    }

    .problem {
        font-size: 2rem;
    }

    .input-group {
        flex-direction: column;
    }

    button {
        width: 100%;
    }

    .operations-grid {
        grid-template-columns: 1fr;
    }

    .difficulty-selector,
    .time-selector {
        flex-direction: column;
    }

    .home-title {
        font-size: 2.5rem;
    }
}

#operationSpan {
    color: var(--primary);
    font-weight: 700;
}

body.dark #operationSpan {
    color: var(--primary-light);
}


input[type="checkbox"] {
    display: none;
}