:root[data-theme="dark"] {
    --bg-color: #000000;
    --text-color: #ffffff;
    --border-color: #38383a;
    --header-bg: rgba(28, 28, 30, 0.8);
    --card-bg: rgba(44, 44, 46, 0.8);
    --nav-bg: rgba(28, 28, 30, 0.9);
    --button-bg: #0a84ff;
    --button-hover: #0071e3;
    --task-pending: #ff9f0a;
    --task-completed: #30d158;
    --icon-filter: invert(1);
}

:root[data-theme="light"] {
    --bg-color: #f2f2f7;
    --text-color: #000000;
    --border-color: rgba(60, 60, 67, 0.1);
    --header-bg: rgba(255, 255, 255, 0.8);
    --card-bg: rgba(255, 255, 255, 0.8);
    --nav-bg: rgba(255, 255, 255, 0.9);
    --button-bg: #007AFF;
    --button-hover: #0056b3;
    --task-pending: #ff9500;
    --task-completed: #34c759;
    --icon-filter: invert(0);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Helvetica Neue', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding: 16px;
    -webkit-font-smoothing: antialiased;
    padding-bottom: 80px;
}

nav {
    background-color: var(--nav-bg);
    padding: max(1rem, env(safe-area-inset-top)) 1rem 1rem;
    position: fixed;
    width: 100%;
    height: auto;
    min-height: 44px;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-bottom: 0.5px solid var(--border-color);
    box-sizing: border-box;
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
    margin: 8px;
    padding: 0;
    gap: 12px;
}

nav ul li {
    margin: 0;
}

nav ul li a {
    text-decoration: none;
    color: var(--button-bg);
    font-size: 15px;
    font-weight: 400;
    padding: 8px 12px;
    border-radius: 8px;
    transition: background-color 0.2s;
    white-space: nowrap;
}

nav ul li a:active {
    opacity: 0.7;
}

.header {
    text-align: center;
    margin-bottom: 20px;
    padding: 20px 16px;
    background: var(--header-bg);
    border-radius: 16px;
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--border-color);
    margin-top: 70px;
}

.header h1 {
    margin: 0;
    font-size: 24px;
    font-weight: 700;
}

.tasks-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
    padding: 20px;
}

.day-card {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 16px;
    border: 1px solid var(--border-color);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.day-header {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 12px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--border-color);
}

.task-item {
    display: flex;
    align-items: center;
    padding: 8px 0;
    border-bottom: 1px solid var(--border-color);
}

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

.task-checkbox {
    margin-right: 12px;
}

.task-content {
    flex-grow: 1;
}

.task-title {
    font-weight: 500;
    margin-bottom: 4px;
}

.task-due {
    font-size: 12px;
    color: var(--task-pending);
}

.task-completed .task-title {
    text-decoration: line-through;
    opacity: 0.7;
}

.task-completed .task-due {
    color: var(--task-completed);
}

#theme-toggle {
    position: fixed;
    top: max(12px, env(safe-area-inset-top));
    right: max(12px, env(safe-area-inset-right));
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    display: flex;
    align-items: center;
    z-index: 1001;
}

#theme-toggle img {
    width: 20px;
    height: 20px;
    filter: var(--icon-filter);
}

footer {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background-color: var(--nav-bg);
    padding: 1rem;
    text-align: center;
    font-size: 14px;
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-top: 0.5px solid var(--border-color);
}
@media (max-width: 768px) {
    .header{
        margin-top: 130px;
    }
}