/* ===== CSS Variables ===== */
:root {
    /* Light Mode Colors */
    --bg-primary: #f5f7fa;
    --bg-secondary: #ffffff;
    --bg-card: rgba(255, 255, 255, 0.7);
    --text-primary: #2d3748;
    --text-secondary: #718096;
    --accent-primary: #667eea;
    --accent-secondary: #764ba2;
    --accent-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --border-color: rgba(0, 0, 0, 0.1);
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 20px 60px rgba(0, 0, 0, 0.15);

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;

    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
}

/* Dark Mode Colors */
[data-theme="dark"] {
    --bg-primary: #1a202c;
    --bg-secondary: #2d3748;
    --bg-card: rgba(45, 55, 72, 0.7);
    --text-primary: #f7fafc;
    --text-secondary: #cbd5e0;
    --border-color: rgba(255, 255, 255, 0.1);
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 20px 60px rgba(0, 0, 0, 0.4);
}

/* ===== Reset & Base Styles ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background 0.3s ease, color 0.3s ease;
    min-height: 100vh;
}

/* ===== Theme Toggle ===== */
.theme-toggle {
    position: fixed;
    top: 2rem;
    right: 2rem;
    width: 60px;
    height: 60px;
    border-radius: 50%;
    border: none;
    background: var(--accent-gradient);
    color: white;
    font-size: 1.5rem;
    cursor: pointer;
    box-shadow: var(--shadow);
    z-index: 1000;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-lg);
}

.theme-toggle .moon-icon {
    display: none;
}

[data-theme="dark"] .theme-toggle .sun-icon {
    display: none;
}

[data-theme="dark"] .theme-toggle .moon-icon {
    display: inline;
}

/* ===== Container ===== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* ===== Hero Section ===== */
.hero {
    padding: var(--spacing-xl) 0;
    text-align: center;
    background: var(--accent-gradient);
    color: white;
    clip-path: polygon(0 0, 100% 0, 100% 85%, 0 100%);
    margin-bottom: var(--spacing-xl);
}

.hero-title {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 800;
    margin-bottom: var(--spacing-sm);
    animation: fadeInUp 0.8s ease;
}

.hero-subtitle {
    font-size: clamp(1rem, 2vw, 1.25rem);
    opacity: 0.95;
    margin-bottom: var(--spacing-lg);
    animation: fadeInUp 0.8s ease 0.2s backwards;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: var(--spacing-lg);
    flex-wrap: wrap;
    animation: fadeInUp 0.8s ease 0.4s backwards;
}

.stat {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: var(--spacing-md);
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border-radius: var(--radius-md);
    min-width: 120px;
}

.stat-value {
    font-size: 2rem;
    font-weight: 700;
}

.stat-label {
    font-size: 0.875rem;
    opacity: 0.9;
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* ===== Features Section ===== */
.features {
    padding: var(--spacing-xl) 0;
}

.section-title {
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: var(--spacing-xl);
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* ===== Feature Cards ===== */
.feature-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
    box-shadow: var(--shadow);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    animation: fadeInUp 0.6s ease;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.feature-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-md);
}

.feature-header h3 {
    font-size: 1.5rem;
    color: var(--text-primary);
}

.feature-toggle {
    padding: 0.5rem 1.5rem;
    background: var(--accent-gradient);
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-weight: 600;
    transition: transform 0.2s ease;
}

.feature-toggle:hover {
    transform: scale(1.05);
}

.feature-content {
    display: none;
    animation: slideDown 0.3s ease;
}

.feature-content.active {
    display: block;
}

/* ===== Calculator ===== */
.calculator {
    max-width: 400px;
    margin: 0 auto;
}

.calculator-display {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    text-align: right;
    font-size: 2.5rem;
    font-weight: 300;
    margin-bottom: var(--spacing-md);
    border: 1px solid var(--border-color);
    min-height: 80px;
    display: flex;
    align-items: center;
    justify-content: flex-end;
    word-wrap: break-word;
    word-break: break-all;
}

.calculator-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-sm);
}

.calc-btn {
    padding: var(--spacing-md);
    font-size: 1.25rem;
    border: 1px solid var(--border-color);
    background: var(--bg-secondary);
    color: var(--text-primary);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.2s ease;
    font-weight: 500;
}

.calc-btn:hover {
    background: var(--accent-primary);
    color: white;
    transform: scale(1.05);
}

.calc-btn:active {
    transform: scale(0.95);
}

.calc-btn-operator {
    background: var(--accent-primary);
    color: white;
}

.calc-btn-equals {
    background: var(--accent-secondary);
    color: white;
}

.calc-btn-clear {
    background: #ef4444;
    color: white;
}

.calc-btn-zero {
    grid-column: span 2;
}

/* ===== Todo App ===== */
.todo-app {
    max-width: 600px;
    margin: 0 auto;
}

.todo-input-container {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.todo-input {
    flex: 1;
    padding: var(--spacing-sm) var(--spacing-md);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.todo-input:focus {
    outline: none;
    border-color: var(--accent-primary);
}

.btn-primary {
    padding: var(--spacing-sm) var(--spacing-lg);
    background: var(--accent-gradient);
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s ease;
}

.btn-primary:hover {
    transform: scale(1.05);
}

.todo-filters {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
    justify-content: center;
}

.filter-btn {
    padding: 0.5rem 1rem;
    background: transparent;
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.3s ease;
}

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

.todo-list {
    list-style: none;
    margin-bottom: var(--spacing-md);
}

.todo-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    margin-bottom: var(--spacing-sm);
    animation: slideIn 0.3s ease;
}

.todo-item.completed .todo-text {
    text-decoration: line-through;
    opacity: 0.6;
}

.todo-checkbox {
    width: 20px;
    height: 20px;
    cursor: pointer;
}

.todo-text {
    flex: 1;
    color: var(--text-primary);
}

.todo-delete {
    padding: 0.25rem 0.75rem;
    background: #ef4444;
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 0.875rem;
    transition: transform 0.2s ease;
}

.todo-delete:hover {
    transform: scale(1.1);
}

.todo-stats {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
}

.btn-text {
    background: none;
    border: none;
    color: var(--accent-primary);
    cursor: pointer;
    text-decoration: underline;
}

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

/* ===== Color Palette Generator ===== */
.color-generator {
    text-align: center;
}

.color-palette {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
}

.color-item {
    aspect-ratio: 1;
    border-radius: var(--radius-md);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: transform 0.3s ease;
    position: relative;
    overflow: hidden;
}

.color-item:hover {
    transform: scale(1.05);
}

.color-code {
    background: rgba(0, 0, 0, 0.6);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-family: monospace;
    font-weight: 600;
}

.color-copied {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: rgba(0, 0, 0, 0.8);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    animation: fadeOut 1s ease;
}

/* ===== Quote Generator ===== */
.quote-generator {
    max-width: 700px;
    margin: 0 auto;
    text-align: center;
}

.quote-display {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    border-left: 4px solid var(--accent-primary);
    margin-bottom: var(--spacing-lg);
}

#quote-text {
    font-size: 1.25rem;
    font-style: italic;
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
    line-height: 1.8;
}

#quote-author {
    display: block;
    color: var(--text-secondary);
    font-weight: 600;
}

/* ===== Typing Test ===== */
.typing-test {
    max-width: 800px;
    margin: 0 auto;
}

.typing-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.stat-item {
    background: var(--bg-secondary);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    text-align: center;
    border: 1px solid var(--border-color);
}

.stat-item .stat-label {
    display: block;
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 0.25rem;
}

.stat-item .stat-value {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.typing-text {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    font-size: 1.25rem;
    line-height: 2;
    margin-bottom: var(--spacing-md);
    border: 1px solid var(--border-color);
    user-select: none;
}

.typing-text .correct {
    color: #10b981;
}

.typing-text .incorrect {
    color: #ef4444;
    background: rgba(239, 68, 68, 0.1);
}

.typing-text .current {
    background: var(--accent-primary);
    color: white;
}

.typing-input {
    width: 100%;
    padding: var(--spacing-md);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 1rem;
    font-family: inherit;
    resize: vertical;
    min-height: 100px;
    margin-bottom: var(--spacing-md);
}

.typing-input:focus {
    outline: none;
    border-color: var(--accent-primary);
}

.typing-input:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* ===== Footer ===== */
.footer {
    background: var(--bg-secondary);
    padding: var(--spacing-xl) 0;
    text-align: center;
    margin-top: var(--spacing-xl);
    border-top: 1px solid var(--border-color);
}

.footer a {
    color: var(--accent-primary);
    text-decoration: none;
    font-weight: 600;
}

.footer a:hover {
    text-decoration: underline;
}

.footer-note {
    margin-top: var(--spacing-sm);
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* ===== Animations ===== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes slideDown {
    from {
        opacity: 0;
        max-height: 0;
    }
    to {
        opacity: 1;
        max-height: 2000px;
    }
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(-20px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes fadeOut {
    from {
        opacity: 1;
    }
    to {
        opacity: 0;
    }
}

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
    .theme-toggle {
        top: 1rem;
        right: 1rem;
        width: 50px;
        height: 50px;
        font-size: 1.25rem;
    }

    .hero {
        padding: var(--spacing-lg) 0;
    }

    .hero-stats {
        flex-direction: column;
        align-items: stretch;
    }

    .stat {
        width: 100%;
    }

    .calculator-buttons {
        gap: 0.5rem;
    }

    .calc-btn {
        padding: var(--spacing-sm);
        font-size: 1rem;
    }

    .feature-header {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-sm);
    }

    .feature-toggle {
        width: 100%;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }

    .section-title {
        font-size: 1.75rem;
    }

    .calculator-display {
        font-size: 1.75rem;
    }

    .color-palette {
        grid-template-columns: repeat(2, 1fr);
    }
}