:root {
    --primary: #6366f1;
    --primary-hover: #4f46e5;
    --bg: #0f172a;
    --card-bg: rgba(30, 41, 59, 0.7);
    --text: #f8fafc;
    --text-muted: #94a3b8;
    --accent: #10b981;
    --danger: #ef4444;
    --glass-border: rgba(255, 255, 255, 0.1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
}

body {
    background: radial-gradient(circle at top left, #1e1b4b, #0f172a);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 2rem;
}

.container {
    width: 100%;
    max-width: 500px;
    background: var(--card-bg);
    backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: 24px;
    padding: 2.5rem;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    animation: fadeIn 0.6s ease-out;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

h1 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 2rem;
    text-align: center;
    background: linear-gradient(to right, #818cf8, #c084fc);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

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

input[type="text"] {
    flex: 1;
    background: rgba(15, 23, 42, 0.6);
    border: 1px solid var(--glass-border);
    border-radius: 12px;
    padding: 0.8rem 1.2rem;
    color: var(--text);
    font-size: 1rem;
    outline: none;
    transition: all 0.3s ease;
}

input[type="text"]:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(99, 102, 241, 0.2);
}

button.btn-add {
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 12px;
    padding: 0.8rem 1.5rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

button.btn-add:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

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

.todo-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem;
    background: rgba(255, 255, 255, 0.03);
    border-radius: 14px;
    margin-bottom: 0.75rem;
    border: 1px solid transparent;
    transition: all 0.3s ease;
    animation: slideIn 0.4s ease-out forwards;
}

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

.todo-item:hover {
    background: rgba(255, 255, 255, 0.05);
    border-color: var(--glass-border);
    transform: scale(1.02);
}

.todo-content {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex: 1;
}

.checkbox {
    width: 20px;
    height: 20px;
    border-radius: 6px;
    border: 2px solid var(--primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
}

.checkbox.checked {
    background: var(--primary);
}

.checkbox.checked::after {
    content: '✓';
    color: white;
    font-size: 12px;
}

.task-text {
    font-size: 1.05rem;
    transition: all 0.3s ease;
}

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

.btn-delete {
    background: transparent;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 8px;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.btn-delete:hover {
    color: var(--danger);
    background: rgba(239, 68, 68, 0.1);
}

/* Scrollbar styling */
::-webkit-scrollbar {
    width: 8px;
}
::-webkit-scrollbar-track {
    background: transparent;
}
::-webkit-scrollbar-thumb {
    background: var(--glass-border);
    border-radius: 10px;
}
::-webkit-scrollbar-thumb:hover {
    background: rgba(255, 255, 255, 0.2);
}