@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap');

:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --secondary: #8b5cf6;
    --success: #10b981;
    --danger: #ef4444;
    --warning: #f59e0b;
    --dark: #0f172a;
    --dark-light: #1e293b;
    --dark-lighter: #334155;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --border: #475569;
    --shadow: rgba(0, 0, 0, 0.3);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 50%, #0f172a 100%);
    min-height: 100vh;
    color: var(--text);
    padding: 20px;
    position: relative;
    overflow-x: hidden;
}

body::before {
    content: '';
    position: fixed;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(99, 102, 241, 0.1) 0%, transparent 50%);
    animation: rotate 30s linear infinite;
    pointer-events: none;
    z-index: 0;
}

@keyframes rotate {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

.container {
    max-width: 800px;
    margin: 0 auto;
    position: relative;
    z-index: 1;
}

header {
    text-align: center;
    margin-bottom: 40px;
    animation: fadeInDown 0.6s ease-out;
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

h1 {
    font-size: 3rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 10px;
    text-shadow: 0 0 30px rgba(99, 102, 241, 0.3);
}

.subtitle {
    color: var(--text-muted);
    font-size: 1.1rem;
    font-weight: 300;
}

.todo-card {
    background: rgba(30, 41, 59, 0.6);
    backdrop-filter: blur(20px);
    border-radius: 24px;
    padding: 30px;
    box-shadow: 0 20px 60px var(--shadow);
    border: 1px solid rgba(255, 255, 255, 0.1);
    animation: fadeInUp 0.6s ease-out;
}

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

.input-group {
    display: flex;
    gap: 12px;
    margin-bottom: 30px;
}

#todoInput {
    flex: 1;
    padding: 16px 20px;
    background: rgba(15, 23, 42, 0.8);
    border: 2px solid var(--border);
    border-radius: 12px;
    color: var(--text);
    font-size: 1rem;
    font-family: inherit;
    transition: all 0.3s ease;
}

#todoInput:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.2);
    background: rgba(15, 23, 42, 1);
}

#todoInput::placeholder {
    color: var(--text-muted);
}

.btn {
    padding: 16px 32px;
    border: none;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    font-family: inherit;
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.2);
    transform: translate(-50%, -50%);
    transition: width 0.6s, height 0.6s;
}

.btn:hover::before {
    width: 300px;
    height: 300px;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: white;
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.6);
}

.btn-primary:active {
    transform: translateY(0);
}

.stats {
    display: flex;
    gap: 15px;
    margin-bottom: 25px;
    flex-wrap: wrap;
}

.stat-item {
    flex: 1;
    min-width: 120px;
    padding: 15px;
    background: rgba(15, 23, 42, 0.6);
    border-radius: 12px;
    border: 1px solid var(--border);
    text-align: center;
    transition: all 0.3s ease;
}

.stat-item:hover {
    transform: translateY(-3px);
    border-color: var(--primary);
    box-shadow: 0 5px 15px rgba(99, 102, 241, 0.3);
}

.stat-number {
    font-size: 1.8rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-top: 5px;
}

.todo-list {
    list-style: none;
}

.todo-item {
    background: rgba(15, 23, 42, 0.6);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 18px 20px;
    margin-bottom: 12px;
    display: flex;
    align-items: center;
    gap: 15px;
    transition: all 0.3s ease;
    animation: slideIn 0.4s ease-out;
}

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

.todo-item:hover {
    border-color: var(--primary);
    transform: translateX(5px);
    box-shadow: 0 5px 20px rgba(99, 102, 241, 0.2);
}

.todo-checkbox {
    width: 24px;
    height: 24px;
    border: 2px solid var(--border);
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.3s ease;
    flex-shrink: 0;
    position: relative;
}

.todo-checkbox:hover {
    border-color: var(--primary);
    transform: scale(1.1);
}

.todo-item.completed .todo-checkbox {
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    border-color: var(--primary);
}

.todo-item.completed .todo-checkbox::after {
    content: '✓';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: white;
    font-size: 14px;
    font-weight: bold;
}

.todo-text {
    flex: 1;
    font-size: 1rem;
    color: var(--text);
    transition: all 0.3s ease;
    word-break: break-word;
}

.todo-item.completed .todo-text {
    text-decoration: line-through;
    color: var(--text-muted);
    opacity: 0.6;
}

.todo-actions {
    display: flex;
    gap: 8px;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.todo-item:hover .todo-actions {
    opacity: 1;
}

.btn-icon {
    width: 36px;
    height: 36px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    transition: all 0.3s ease;
    background: rgba(255, 255, 255, 0.05);
}

.btn-icon:hover {
    transform: scale(1.1);
}

.btn-edit {
    color: var(--warning);
}

.btn-edit:hover {
    background: var(--warning);
    color: white;
}

.btn-delete {
    color: var(--danger);
}

.btn-delete:hover {
    background: var(--danger);
    color: white;
}

.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-muted);
}

.empty-state-icon {
    font-size: 4rem;
    margin-bottom: 20px;
    opacity: 0.5;
}

.empty-state-text {
    font-size: 1.2rem;
    font-weight: 500;
}

.loading {
    text-align: center;
    padding: 40px;
    color: var(--text-muted);
}

.spinner {
    border: 3px solid rgba(255, 255, 255, 0.1);
    border-top: 3px solid var(--primary);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    animation: spin 1s linear infinite;
    margin: 0 auto 15px;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.notification {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 16px 24px;
    border-radius: 12px;
    color: white;
    font-weight: 500;
    box-shadow: 0 10px 30px var(--shadow);
    animation: slideInRight 0.4s ease-out;
    z-index: 1000;
    max-width: 300px;
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(100px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.notification.success {
    background: linear-gradient(135deg, var(--success), #059669);
}

.notification.error {
    background: linear-gradient(135deg, var(--danger), #dc2626);
}

@media (max-width: 768px) {
    h1 {
        font-size: 2rem;
    }
    
    .subtitle {
        font-size: 1rem;
    }
    
    .todo-card {
        padding: 20px;
    }
    
    .input-group {
        flex-direction: column;
    }
    
    .btn-primary {
        width: 100%;
    }
    
    .stats {
        flex-direction: column;
    }
    
    .stat-item {
        min-width: 100%;
    }
    
    .todo-actions {
        opacity: 1;
    }
}