body {
    font-family: 'Segoe UI', Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    min-height: 100vh;
    margin: 0;
    transition: background-color 0.3s ease;
}

/* Theme Colors */
body.green { background-color: #e8f5e9; }
body.blue { background-color: #e3f2fd; }
body.pink { background-color: #fce4ec; }
body.yellow { background-color: #fffde7; }
body.purple { background-color: #f3e5f5; }
body.orange { background-color: #fff3e0; }
body.cyan { background-color: #e0f7fa; }
body.red { background-color: #ffebee; }

.container {
    background: #ffffff;
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
    width: 600px;
    max-width: 90%;
    margin: 20px;
    transition: background-color 0.3s ease, transform 0.3s ease;
    box-sizing: border-box;
}

/* Theme-specific container background */
body.green .container { background: #f1f8e9; }
body.blue .container { background: #e8f5fd; }
body.pink .container { background: #f8e1ea; }
body.yellow .container { background: #fff9c4; }
body.purple .container { background: #f3e8ff; }
body.orange .container { background: #ffedd5; }
body.cyan .container { background: #e0f7fa; }
body.red .container { background: #ffebee; }

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

h1 {
    color: #2c3e50;
    font-size: 28px;
    margin: 0;
    transition: color 0.3s ease;
}

body.green h1 { color: #2e7d32; }
body.blue h1 { color: #1565c0; }
body.pink h1 { color: #ad1457; }
body.yellow h1 { color: #f9a825; }
body.purple h1 { color: #6a1b9a; }
body.orange h1 { color: #ef6c00; }
body.cyan h1 { color: #00838f; }
body.red h1 { color: #c62828; }

.input-section {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: 20px;
    width: 100%;
    box-sizing: border-box;
}

input, select {
    padding: 10px;
    border: 1px solid #b3cde0;
    border-radius: 6px;
    font-size: 16px;
    box-sizing: border-box;
    transition: border-color 0.3s ease, transform 0.2s ease;
}

input:hover, select:hover {
    border-color: #90caf9;
    transform: scale(1.02);
}

input[type="text"] {
    flex: 1;
    min-width: 200px;
}

input[type="datetime-local"] {
    min-width: 180px;
    max-width: 100%;
}

button {
    padding: 10px 16px;
    border: none;
    color: white;
    border-radius: 6px;
    cursor: pointer;
    font-size: 16px;
    transition: background-color 0.3s ease, transform 0.2s ease;
}

/* Button colors contrasting with themes */
body.green button { background-color: #e91e63; }
body.blue button { background-color: #f57c00; }
body.pink button { background-color: #388e3c; }
body.yellow button { background-color: #d81b60; }
body.purple button { background-color: #0288d1; }
body.orange button { background-color: #6a1b9a; }
body.cyan button { background-color: #d81b60; }
body.red button { background-color: #388e3c; }

button:hover {
    transform: scale(1.05);
}

body.green button:hover { background-color: #c2185b; }
body.blue button:hover { background-color: #ef6c00; }
body.pink button:hover { background-color: #2e7d32; }
body.yellow button:hover { background-color: #c2185b; }
body.purple button:hover { background-color: #0277bd; }
body.orange button:hover { background-color: #4a148c; }
body.cyan button:hover { background-color: #c2185b; }
body.red button:hover { background-color: #2e7d32; }

.filters {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: 20px;
}

.filters button {
    flex: 1;
    transition: background-color 0.3s ease, transform 0.2s ease;
}

.filters button:hover {
    transform: scale(1.05);
}

.search-section {
    margin-bottom: 20px;
    width: 100%;
}

#searchInput {
    width: 100%;
    font-size: 16px;
    box-sizing: border-box;
}

ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

li {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px;
    border-bottom: 1px solid #dfe6e9;
    border-radius: 6px;
    margin-bottom: 8px;
    animation: fadeIn 0.5s ease-in;
    transition: background-color 0.3s ease, transform 0.2s ease;
}

li:hover {
    transform: translateX(5px);
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

body.green li { border-bottom: 1px solid #c8e6c9; }
body.blue li { border-bottom: 1px solid #bbdefb; }
body.pink li { border-bottom: 1px solid #f8bbd0; }
body.yellow li { border-bottom: 1px solid #fff9c4; }
body.purple li { border-bottom: 1px solid #e1bee7; }
body.orange li { border-bottom: 1px solid #ffccbc; }
body.cyan li { border-bottom: 1px solid #b2ebf2; }
body.red li { border-bottom: 1px solid #ffcdd2; }

li.completed span {
    text-decoration: line-through;
    color: #95a5a6;
}

.actions button {
    margin-left: 8px;
}

.priority-low { color: #2ecc71; }
.priority-medium { color: #f1c40f; }
.priority-high { color: #e74c3c; }

.category-work { background: #e8f4f8; }
.category-personal { background: #d4efdf; }
.category-study { background: #fce4d6; }

body.green .category-work { background: #dcedc8; }
body.green .category-personal { background: #c5e1a5; }
body.green .category-study { background: #aed581; }

body.blue .category-work { background: #bbdefb; }
body.blue .category-personal { background: #90caf9; }
body.blue .category-study { background: #64b5f6; }

body.pink .category-work { background: #f8bbd0; }
body.pink .category-personal { background: #f48fb1; }
body.pink .category-study { background: #f06292; }

body.yellow .category-work { background: #fff9c4; }
body.yellow .category-personal { background: #fff59d; }
body.yellow .category-study { background: #fff176; }

body.purple .category-work { background: #e1bee7; }
body.purple .category-personal { background: #ce93d8; }
body.purple .category-study { background: #ba68c8; }

body.orange .category-work { background: #ffccbc; }
body.orange .category-personal { background: #ffab91; }
body.orange .category-study { background: #ff8a65; }

body.cyan .category-work { background: #b2ebf2; }
body.cyan .category-personal { background: #80deea; }
body.cyan .category-study { background: #4dd0e1; }

body.red .category-work { background: #ffcdd2; }
body.red .category-personal { background: #ef9a9a; }
body.red .category-study { background: #e57373; }

.stats {
    margin-bottom: 20px;
    padding: 12px;
    border-radius: 6px;
    font-size: 16px;
    animation: slideIn 0.5s ease;
}

body.green .stats { background: #dcedc8; }
body.blue .stats { background: #bbdefb; }
body.pink .stats { background: #f8bbd0; }
body.yellow .stats { background: #fff9c4; }
body.purple .stats { background: #e1bee7; }
body.orange .stats { background: #ffccbc; }
body.cyan .stats { background: #b2ebf2; }
body.red .stats { background: #ffcdd2; }

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes slideIn {
    from { opacity: 0; transform: translateX(-20px); }
    to { opacity: 1; transform: translateX(0); }
}

/* Theme Selector */
#themeSelect {
    padding: 8px;
    border-radius: 6px;
    border: 1px solid #b3cde0;
    background: #ffffff;
    font-size: 16px;
    transition: transform 0.2s ease;
}

#themeSelect:hover {
    transform: scale(1.02);
}

/* Mobile Responsiveness */
@media (max-width: 600px) {
    .container {
        padding: 20px;
        margin: 10px;
        width: 100%;
        max-width: 100%;
    }
    .input-section {
        flex-direction: column;
        gap: 8px;
    }
    input, select, button {
        width: 100%;
        max-width: 100%;
    }
    input[type="datetime-local"] {
        width: 100%;
    }
    .filters {
        flex-direction: column;
        gap: 8px;
    }
    .filters button {
        width: 100%;
    }
    h1 {
        font-size: 24px;
    }
    .actions button {
        padding: 8px 12px;
        font-size: 14px;
    }
}