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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
}

/* Header Styles */
header {
    background: rgba(255, 255, 255, 0.95);
    padding: 2rem;
    text-align: center;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

header h1 {
    color: #667eea;
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.subtitle {
    color: #666;
    font-size: 1rem;
}

/* Navigation Styles */
#navigation {
    background: rgba(255, 255, 255, 0.9);
    padding: 1rem;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 0.5rem;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.nav-btn {
    padding: 0.75rem 1.5rem;
    border: 2px solid #667eea;
    background: white;
    color: #667eea;
    font-size: 1rem;
    cursor: pointer;
    border-radius: 25px;
    transition: all 0.3s ease;
    font-weight: 600;
}

.nav-btn:hover {
    background: #667eea;
    color: white;
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(102, 126, 234, 0.3);
}

.nav-btn.active {
    background: #667eea;
    color: white;
}

/* Main Content Styles */
#main-content {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 2rem;
}

.content-section {
    display: none;
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: 0 5px 20px rgba(0, 0, 0, 0.1);
    animation: fadeIn 0.5s ease;
}

.content-section.active {
    display: block;
}

.content-section h2 {
    color: #667eea;
    margin-bottom: 1.5rem;
    font-size: 2rem;
}

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

/* Calculator Styles */
.calculator {
    max-width: 400px;
    margin: 0 auto;
}

.calc-display {
    background: #f5f5f5;
    padding: 2rem;
    text-align: right;
    font-size: 2.5rem;
    border-radius: 10px;
    margin-bottom: 1rem;
    min-height: 80px;
    word-wrap: break-word;
    border: 2px solid #667eea;
}

.calc-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.5rem;
}

.calc-btn {
    padding: 1.5rem;
    font-size: 1.5rem;
    border: 2px solid #ddd;
    background: white;
    cursor: pointer;
    border-radius: 10px;
    transition: all 0.2s ease;
}

.calc-btn:hover {
    background: #667eea;
    color: white;
    border-color: #667eea;
    transform: scale(1.05);
}

.calc-btn:active {
    transform: scale(0.95);
}

.calc-zero {
    grid-column: span 2;
}

.calc-equals {
    grid-row: span 2;
    background: #667eea;
    color: white;
}

/* Todo List Styles */
.todo-container {
    max-width: 600px;
    margin: 0 auto;
}

.todo-input-group {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.todo-input-group input {
    flex: 1;
    padding: 0.75rem;
    font-size: 1rem;
    border: 2px solid #ddd;
    border-radius: 8px;
}

.todo-input-group button {
    padding: 0.75rem 2rem;
    background: #667eea;
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: background 0.3s ease;
}

.todo-input-group button:hover {
    background: #5568d3;
}

.todo-list {
    list-style: none;
    margin-bottom: 1rem;
}

.todo-item {
    display: flex;
    align-items: center;
    padding: 1rem;
    background: #f9f9f9;
    margin-bottom: 0.5rem;
    border-radius: 8px;
    transition: all 0.3s ease;
}

.todo-item:hover {
    background: #f0f0f0;
    transform: translateX(5px);
}

.todo-item.completed .todo-text {
    text-decoration: line-through;
    color: #999;
}

.todo-item input[type="checkbox"] {
    margin-right: 1rem;
    width: 1.25em;
    height: 1.25em;
    cursor: pointer;
}

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

.todo-delete {
    background: #ff4757;
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 5px;
    cursor: pointer;
    transition: background 0.3s ease;
}

.todo-delete:hover {
    background: #ee5a6f;
}

.todo-stats {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem;
    background: #f5f5f5;
    border-radius: 8px;
}

.todo-stats button {
    background: #764ba2;
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 5px;
    cursor: pointer;
    font-size: 0.9rem;
}

.todo-stats button:hover {
    background: #633d8a;
}

/* Converter Styles */
.converter-container {
    max-width: 600px;
    margin: 0 auto;
}

.converter-type {
    margin-bottom: 2rem;
    text-align: center;
}

.converter-type label {
    font-weight: 600;
    margin-right: 1rem;
    font-size: 1.1rem;
}

.converter-type select {
    padding: 0.75rem;
    font-size: 1rem;
    border: 2px solid #667eea;
    border-radius: 8px;
    cursor: pointer;
}

.converter-inputs {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.converter-input {
    flex: 1;
    min-width: 200px;
}

.converter-input input,
.converter-input select {
    width: 100%;
    padding: 0.75rem;
    font-size: 1rem;
    border: 2px solid #ddd;
    border-radius: 8px;
    margin-bottom: 0.5rem;
}

.converter-arrow {
    font-size: 2rem;
    color: #667eea;
    font-weight: bold;
}

/* Weather Styles */
.weather-container {
    max-width: 600px;
    margin: 0 auto;
}

.weather-input-group {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 2rem;
}

.weather-input-group input {
    flex: 1;
    padding: 0.75rem;
    font-size: 1rem;
    border: 2px solid #ddd;
    border-radius: 8px;
}

.weather-input-group button {
    padding: 0.75rem 2rem;
    background: #667eea;
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
}

.weather-input-group button:hover {
    background: #5568d3;
}

.weather-display {
    padding: 2rem;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border-radius: 15px;
    color: white;
    min-height: 200px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.weather-hint {
    font-size: 1.2rem;
    text-align: center;
}

.weather-info {
    text-align: center;
}

.weather-city {
    font-size: 2rem;
    font-weight: bold;
    margin-bottom: 1rem;
}

.weather-temp {
    font-size: 3rem;
    font-weight: bold;
    margin: 1rem 0;
}

.weather-desc {
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.weather-details {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-top: 1rem;
    flex-wrap: wrap;
}

.weather-detail {
    text-align: center;
}

.weather-detail-label {
    font-size: 0.9rem;
    opacity: 0.8;
}

.weather-detail-value {
    font-size: 1.2rem;
    font-weight: bold;
}

/* Tips Styles */
.tips-container {
    max-width: 700px;
    margin: 0 auto;
}

.tips-display {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 3rem;
    border-radius: 15px;
    margin-bottom: 2rem;
    min-height: 200px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
}

.tip-text {
    font-size: 1.5rem;
    line-height: 1.8;
}

.tips-btn {
    display: block;
    width: 100%;
    padding: 1rem;
    background: #667eea;
    color: white;
    border: none;
    border-radius: 10px;
    font-size: 1.2rem;
    font-weight: 600;
    cursor: pointer;
    margin-bottom: 1rem;
    transition: background 0.3s ease;
}

.tips-btn:hover {
    background: #5568d3;
}

.tips-category {
    text-align: center;
}

.tips-category label {
    font-weight: 600;
    margin-right: 1rem;
    font-size: 1.1rem;
}

.tips-category select {
    padding: 0.75rem;
    font-size: 1rem;
    border: 2px solid #667eea;
    border-radius: 8px;
    cursor: pointer;
}

/* Footer Styles */
footer {
    background: rgba(255, 255, 255, 0.95);
    text-align: center;
    padding: 2rem;
    margin-top: 2rem;
    color: #666;
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.8rem;
    }
    
    #navigation {
        padding: 0.5rem;
    }
    
    .nav-btn {
        padding: 0.5rem 1rem;
        font-size: 0.9rem;
    }
    
    #main-content {
        padding: 1rem;
        margin: 1rem auto;
    }
    
    .content-section {
        padding: 1.5rem;
    }
    
    .calc-display {
        font-size: 2rem;
        padding: 1.5rem;
    }
    
    .calc-btn {
        padding: 1rem;
        font-size: 1.2rem;
    }
    
    .converter-inputs {
        flex-direction: column;
    }
    
    .converter-arrow {
        transform: rotate(90deg);
    }
    
    .tip-text {
        font-size: 1.2rem;
    }
}