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

:root {
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --secondary-color: #6b7280;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --bg-color: #f3f4f6;
    --card-bg: #ffffff;
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --border-color: #e5e7eb;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius: 8px;
    --radius-lg: 12px;
    --transition: all 0.2s ease;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

a {
    color: var(--primary-color);
    text-decoration: none;
    cursor: pointer;
}

a:hover {
    text-decoration: underline;
}

button {
    cursor: pointer;
    font-family: inherit;
    border: none;
    outline: none;
}

input {
    font-family: inherit;
}

/* Utility Classes */
.hidden {
    display: none !important;
}

.error-message {
    color: var(--danger-color);
    font-size: 0.875rem;
    margin-top: 0.5rem;
    display: none;
}

.error-message.show {
    display: block;
}

/* Screen Management */
.screen {
    display: none;
    min-height: 100vh;
}

.screen.active {
    display: block;
}

/* Login / Register Container */
.login-container {
    max-width: 400px;
    margin: 0 auto;
    padding: 2rem 1rem;
    text-align: center;
}

.login-container h1 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.login-container h1 i {
    color: var(--primary-color);
    margin-right: 0.5rem;
}

.login-container p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
}

.form-group {
    margin-bottom: 1.5rem;
    text-align: left;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
    font-size: 0.875rem;
}

.form-group input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 1rem;
    transition: var(--transition);
    background-color: #fff;
}

.form-group input:focus {
    border-color: var(--primary-color);
    outline: none;
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.auth-switch {
    margin-top: 1.5rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.auth-switch a {
    font-weight: 500;
}

/* Buttons */
.btn {
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius);
    font-weight: 500;
    font-size: 0.875rem;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.btn-primary {
    background-color: var(--primary-color);
    color: #fff;
    width: 100%;
}

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

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

.btn-secondary:hover {
    background-color: #f9fafb;
    border-color: var(--text-secondary);
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.75rem;
}

/* Dashboard Header */
.dashboard-header {
    background-color: var(--card-bg);
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow);
}

.user-info {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.user-info i {
    font-size: 1.5rem;
    color: var(--primary-color);
}

.user-info span {
    font-weight: 600;
    font-size: 1rem;
}

.date-display {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Dashboard Content */
.dashboard-content {
    max-width: 800px;
    margin: 2rem auto;
    padding: 0 1rem;
}

.todo-container {
    background-color: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    overflow: hidden;
}

.todo-header {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.todo-header h2 {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.25rem;
    color: var(--text-primary);
}

.todo-header h2 i {
    color: var(--primary-color);
}

.todo-filters {
    display: flex;
    gap: 0.5rem;
}

.filter-btn {
    padding: 0.5rem 1rem;
    border-radius: var(--radius);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    background-color: transparent;
    border: 1px solid transparent;
    transition: var(--transition);
}

.filter-btn:hover {
    color: var(--primary-color);
    background-color: #f3f4f6;
}

.filter-btn.active {
    color: var(--primary-color);
    background-color: #eef2ff;
    border-color: var(--primary-color);
}

/* Add Todo Form */
.add-todo-form {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    gap: 0.75rem;
}

.add-todo-form form {
    display: flex;
    gap: 0.75rem;
    flex: 1;
}

.add-todo-form input {
    flex: 1;
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 0.95rem;
    transition: var(--transition);
}

.add-todo-form input:focus {
    border-color: var(--primary-color);
    outline: none;
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

/* Todo List */
.todo-list {
    padding: 0;
}

.todo-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition);
}

.todo-item:last-child {
    border-bottom: none;
}

.todo-item:hover {
    background-color: #f9fafb;
}

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

.todo-checkbox {
    width: 1.25rem;
    height: 1.25rem;
    cursor: pointer;
    accent-color: var(--success-color);
}

.todo-text {
    flex: 1;
    margin: 0 1rem;
    font-size: 0.95rem;
    word-break: break-word;
}

.todo-actions {
    display: flex;
    gap: 0.5rem;
}

.btn-icon {
    width: 2.5rem;
    height: 2.5rem;
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-secondary);
    transition: var(--transition);
}

.btn-icon:hover {
    background-color: #f3f4f6;
}

.btn-icon.edit:hover {
    color: var(--primary-color);
    background-color: #eef2ff;
}

.btn-icon.delete:hover {
    color: var(--danger-color);
    background-color: #fef2f2;
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-secondary);
}

.empty-state i {
    font-size: 3rem;
    margin-bottom: 1rem;
    color: #d1d5db;
}

.empty-state p {
    font-size: 1rem;
}

/* Toast Notifications */
.toast-container {
    position: fixed;
    top: 1rem;
    right: 1rem;
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    pointer-events: none;
}

.toast {
    background-color: var(--card-bg);
    color: var(--text-primary);
    padding: 1rem 1.5rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    border-left: 4px solid var(--primary-color);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    min-width: 300px;
    pointer-events: auto;
    animation: slideIn 0.3s ease;
}

.toast.success {
    border-left-color: var(--success-color);
}

.toast.error {
    border-left-color: var(--danger-color);
}

.toast.warning {
    border-left-color: var(--warning-color);
}

.toast i {
    font-size: 1.25rem;
}

.toast.success i {
    color: var(--success-color);
}

.toast.error i {
    color: var(--danger-color);
}

.toast.warning i {
    color: var(--warning-color);
}

.toast-message {
    font-size: 0.875rem;
    font-weight: 500;
}

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

/* Responsive Design */
@media (max-width: 640px) {
    .login-container {
        padding: 1rem;
    }
    
    .dashboard-header {
        flex-direction: column;
        gap: 1rem;
        align-items: flex-start;
    }
    
    .add-todo-form {
        flex-direction: column;
    }
    
    .todo-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }
    
    .todo-text {
        width: 100%;
        margin: 0;
    }
    
    .todo-actions {
        align-self: flex-end;
    }
}