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

:root {
    --bg-primary: #0f0f0f;
    --bg-secondary: #1a1a1a;
    --bg-tertiary: #252525;
    --bg-hover: #2a2a2a;
    --text-primary: #ffffff;
    --text-secondary: #b3b3b3;
    --text-muted: #808080;
    --accent-primary: #6366f1;
    --accent-primary-hover: #4f46e5;
    --accent-secondary: #8b5cf6;
    --success: #10b981;
    --danger: #ef4444;
    --warning: #f59e0b;
    --border-color: #333333;
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Inter', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--bg-primary);
    background-image: 
        radial-gradient(at 0% 0%, rgba(99, 102, 241, 0.1) 0px, transparent 50%),
        radial-gradient(at 100% 100%, rgba(139, 92, 246, 0.1) 0px, transparent 50%);
    min-height: 100vh;
    padding: 20px;
    color: var(--text-primary);
    line-height: 1.6;
}

.container {
    max-width: 900px;
    margin: 0 auto;
}

header {
    text-align: center;
    margin-bottom: 40px;
    padding: 40px 20px;
}

header h1 {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 12px;
    background: linear-gradient(135deg, var(--accent-primary) 0%, var(--accent-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.02em;
}

.subtitle {
    font-size: 1.1rem;
    color: var(--text-secondary);
    font-weight: 400;
}

.todo-form {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 32px;
    margin-bottom: 32px;
    box-shadow: var(--shadow-md);
    backdrop-filter: blur(10px);
}

.todo-form h2 {
    margin-bottom: 24px;
    color: var(--text-primary);
    font-size: 1.5rem;
    font-weight: 600;
}

.form-group {
    margin-bottom: 24px;
}

.form-group label {
    display: block;
    margin-bottom: 10px;
    font-weight: 500;
    color: var(--text-secondary);
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.form-group input[type="text"],
.form-group textarea {
    width: 100%;
    padding: 14px 16px;
    border: 1px solid var(--border-color);
    border-radius: 10px;
    font-size: 1rem;
    background: var(--bg-tertiary);
    color: var(--text-primary);
    transition: all 0.3s ease;
    font-family: inherit;
}

.form-group input[type="text"]:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
    background: var(--bg-hover);
}

.form-group input[type="text"]::placeholder,
.form-group textarea::placeholder {
    color: var(--text-muted);
}

.checkbox-label {
    display: flex;
    align-items: center;
    cursor: pointer;
    user-select: none;
}

.checkbox-label input[type="checkbox"] {
    width: 20px;
    height: 20px;
    margin-right: 12px;
    cursor: pointer;
    accent-color: var(--accent-primary);
}

.checkbox-label span {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.btn {
    padding: 12px 24px;
    border: none;
    border-radius: 10px;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    font-family: inherit;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent-primary) 0%, var(--accent-secondary) 100%);
    color: white;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
}

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

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--bg-hover);
    border-color: var(--text-muted);
}

.btn-danger {
    background: var(--danger);
    color: white;
    padding: 8px 16px;
    font-size: 0.875rem;
    box-shadow: 0 2px 8px rgba(239, 68, 68, 0.3);
}

.btn-danger:hover {
    background: #dc2626;
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(239, 68, 68, 0.4);
}

.btn-edit {
    background: var(--success);
    color: white;
    padding: 8px 16px;
    font-size: 0.875rem;
    margin-right: 8px;
    box-shadow: 0 2px 8px rgba(16, 185, 129, 0.3);
}

.btn-edit:hover {
    background: #059669;
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.4);
}

.todo-list-container {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 32px;
    box-shadow: var(--shadow-md);
}

.todo-list-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 28px;
    flex-wrap: wrap;
    gap: 20px;
}

.todo-list-header h2 {
    color: var(--text-primary);
    font-size: 1.5rem;
    font-weight: 600;
}

.filter-buttons {
    display: flex;
    gap: 8px;
    background: var(--bg-tertiary);
    padding: 4px;
    border-radius: 10px;
    border: 1px solid var(--border-color);
}

.filter-btn {
    padding: 8px 16px;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    border-radius: 8px;
    cursor: pointer;
    font-weight: 500;
    font-size: 0.875rem;
    transition: all 0.3s ease;
    font-family: inherit;
}

.filter-btn:hover {
    color: var(--text-primary);
    background: var(--bg-hover);
}

.filter-btn.active {
    background: linear-gradient(135deg, var(--accent-primary) 0%, var(--accent-secondary) 100%);
    color: white;
    box-shadow: 0 2px 8px rgba(99, 102, 241, 0.3);
}

.todo-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.todo-item {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 20px 24px;
    transition: all 0.3s ease;
    animation: slideIn 0.3s ease-out;
    position: relative;
    overflow: hidden;
}

.todo-item::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: var(--accent-primary);
    opacity: 0;
    transition: opacity 0.3s ease;
}

.todo-item:hover {
    background: var(--bg-hover);
    border-color: var(--accent-primary);
    transform: translateX(4px);
    box-shadow: var(--shadow-sm);
}

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

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.todo-item.completed {
    opacity: 0.6;
    border-color: var(--success);
}

.todo-item.completed::before {
    background: var(--success);
    opacity: 0.5;
}

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

.todo-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 16px;
}

.todo-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    flex: 1;
    line-height: 1.5;
}

.todo-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 16px;
    margin-top: 16px;
    padding-top: 16px;
    border-top: 1px solid var(--border-color);
}

.todo-actions {
    display: flex;
    gap: 8px;
}

.todo-date {
    font-size: 0.8rem;
    color: var(--text-muted);
    font-weight: 400;
}

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

.empty-state.hidden {
    display: none;
}

.empty-state p {
    font-size: 1.1rem;
}

/* Modal Styles */
.modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.75);
    backdrop-filter: blur(4px);
    animation: fadeIn 0.3s ease;
}

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

.modal-content {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    margin: 5% auto;
    padding: 32px;
    border-radius: 16px;
    width: 90%;
    max-width: 500px;
    box-shadow: var(--shadow-lg);
    animation: slideDown 0.3s ease;
    position: relative;
}

@keyframes slideDown {
    from {
        transform: translateY(-50px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.modal-content h2 {
    color: var(--text-primary);
    margin-bottom: 24px;
    font-size: 1.5rem;
    font-weight: 600;
}

.close {
    color: var(--text-muted);
    float: right;
    font-size: 28px;
    font-weight: 300;
    cursor: pointer;
    line-height: 20px;
    transition: color 0.3s ease;
    position: absolute;
    right: 24px;
    top: 24px;
}

.close:hover {
    color: var(--text-primary);
}

.modal-buttons {
    display: flex;
    gap: 12px;
    margin-top: 24px;
}

.modal-buttons .btn {
    flex: 1;
}

/* Scrollbar Styling */
::-webkit-scrollbar {
    width: 10px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--bg-tertiary);
    border-radius: 5px;
    border: 2px solid var(--bg-primary);
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 2.25rem;
    }

    .todo-form,
    .todo-list-container {
        padding: 24px;
    }

    .todo-list-header {
        flex-direction: column;
        align-items: flex-start;
    }

    .filter-buttons {
        width: 100%;
        justify-content: space-between;
    }

    .filter-btn {
        flex: 1;
    }

    .todo-header {
        flex-direction: column;
        gap: 12px;
    }

    .todo-footer {
        flex-direction: column;
        align-items: flex-start;
    }

    .modal-content {
        width: 95%;
        margin: 10% auto;
        padding: 24px;
    }
}

@media (max-width: 480px) {
    body {
        padding: 12px;
    }

    header {
        padding: 24px 12px;
    }

    header h1 {
        font-size: 1.875rem;
    }

    .todo-form,
    .todo-list-container {
        padding: 20px;
    }
}