:root {
    --primary: #6366f1;
    --primary-hover: #4f46e5;
    --bg-gradient: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    --card-bg: rgba(30, 41, 59, 0.7);
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --border-color: rgba(255, 255, 255, 0.1);
    --glass-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
}

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

body {
    font-family: 'Inter', sans-serif;
    background: var(--bg-gradient);
    background-attachment: fixed;
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    width: 100%;
    max-width: 500px;
    background: var(--card-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--border-color);
    border-radius: 24px;
    padding: 40px;
    box-shadow: var(--glass-shadow);
    animation: fadeIn 0.8s ease-out;
}

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

header {
    margin-bottom: 30px;
}

header h1 {
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: 5px;
    background: linear-gradient(to right, #818cf8, #c084fc);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

#date-display {
    color: var(--text-muted);
    font-size: 0.9rem;
}

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

#todo-input {
    flex: 1;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 14px 20px;
    color: white;
    font-size: 1rem;
    transition: all 0.3s ease;
}

#todo-input:focus {
    outline: none;
    background: rgba(255, 255, 255, 0.1);
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(99, 102, 241, 0.2);
}

#add-btn {
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 12px;
    width: 50px;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    transition: all 0.3s ease;
}

#add-btn:hover {
    background: var(--primary-hover);
    transform: scale(1.05);
}

#todo-list {
    list-style: none;
    margin-bottom: 30px;
    max-height: 400px;
    overflow-y: auto;
    padding-right: 5px;
}

#todo-list::-webkit-scrollbar {
    width: 5px;
}

#todo-list::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 10px;
}

.todo-item {
    display: flex;
    align-items: center;
    padding: 14px;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    margin-bottom: 12px;
    transition: all 0.3s ease;
    animation: slideIn 0.4s ease-out;
}

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

.todo-item:hover {
    background: rgba(255, 255, 255, 0.06);
    transform: translateX(5px);
}

.todo-item.completed {
    opacity: 0.6;
}

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

.checkbox {
    width: 22px;
    height: 22px;
    border: 2px solid var(--primary);
    border-radius: 6px;
    margin-right: 15px;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: all 0.2s ease;
}

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

.checkbox svg {
    color: white;
    display: none;
}

.completed .checkbox svg {
    display: block;
}

.todo-text {
    flex: 1;
    font-size: 1rem;
    cursor: pointer;
}

.delete-btn {
    background: transparent;
    border: none;
    color: #ef4444;
    cursor: pointer;
    opacity: 0;
    transition: all 0.3s ease;
    padding: 5px;
}

.todo-item:hover .delete-btn {
    opacity: 1;
}

.delete-btn:hover {
    transform: scale(1.2);
}

footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-top: 1px solid var(--border-color);
    padding-top: 20px;
}

.stats {
    color: var(--text-muted);
    font-size: 0.85rem;
}

.filters {
    display: flex;
    gap: 8px;
}

.filter-btn {
    background: transparent;
    border: none;
    color: var(--text-muted);
    font-size: 0.85rem;
    cursor: pointer;
    padding: 4px 8px;
    border-radius: 6px;
    transition: all 0.2s ease;
}

.filter-btn:hover {
    color: var(--text-main);
}

.filter-btn.active {
    color: var(--primary);
    background: rgba(99, 102, 241, 0.1);
}