:root {
    --primary-color: #2c3e50;
    --secondary-color: #3498db;
    --accent-color: #e74c3c;
    --background-color: #ecf0f1;
    --text-color: #2c3e50;
    --border-color: #bdc3c7;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --success-color: #27ae60;
}

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

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

.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 20px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

header {
    text-align: center;
    margin-bottom: 40px;
    padding: 30px 0;
    user-select: none;
}

    header h1 {
        color: white;
        font-size: 2.5rem;
        font-weight: 300;
        text-shadow: 2px 2px 4px var(--shadow-color);
        letter-spacing: 1px;
        outline: none;
    }

main {
    flex: 1;
    display: flex;
    justify-content: center;
    align-items: flex-start;
}

.tab-container {
    background: white;
    border-radius: 12px;
    box-shadow: 0 10px 30px var(--shadow-color);
    overflow: hidden;
    width: 100%;
    max-width: 800px;
    animation: slideUp 0.6s ease-out;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.tab-buttons {
    display: flex;
    background: var(--background-color);
    border-bottom: 2px solid var(--border-color);
}

.tab-button {
    flex: 1;
    padding: 18px 20px;
    border: none;
    background: transparent;
    color: var(--text-color);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
    border-bottom: 3px solid transparent;
}

    .tab-button:hover {
        background: rgba(52, 152, 219, 0.1);
        color: var(--secondary-color);
    }

    .tab-button.active {
        background: white;
        color: var(--secondary-color);
        border-bottom-color: var(--secondary-color);
        font-weight: 600;
    }

.tab-content {
    padding: 0;
    position: relative;
    overflow: hidden;
    transition: height 0.3s ease-in-out;
}

.tab-panel {
    display: flex;
    flex-direction: column;
    padding: 40px;
    padding-bottom: 20px;
    opacity: 0;
    visibility: hidden;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    transition: opacity 0.3s ease-in-out, visibility 0.3s ease-in-out;
}

    .tab-panel.active {
        opacity: 1;
        visibility: visible;
        position: relative;
    }

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateX(20px);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.tab-panel h2 {
    color: var(--primary-color);
    margin-bottom: 30px;
    font-size: 1.8rem;
    font-weight: 400;
    border-bottom: 2px solid var(--background-color);
    padding-bottom: 10px;
}

.form-section {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

    .input-group label {
        font-weight: 600;
        color: var(--primary-color);
        font-size: 0.95rem;
        letter-spacing: 0.5px;
    }

    .input-group input {
        padding: 14px 16px;
        border: 2px solid var(--border-color);
        border-radius: 8px;
        font-size: 1rem;
        transition: all 0.3s ease;
        background: white;
    }

        .input-group input:focus {
            outline: none;
            border-color: var(--secondary-color);
            box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
            transform: translateY(-1px);
        }

        .input-group input:hover {
            border-color: var(--secondary-color);
        }

        .input-group input[readonly] {
            background: var(--background-color);
            color: var(--text-color);
            cursor: not-allowed;
        }

    .input-group select {
        appearance: base-select;
        padding: 14px 16px;
        border: 2px solid var(--border-color);
        border-radius: 8px;
        font-size: 1rem;
        transition: all 0.3s ease;
        background: white;
    }

        .input-group select:focus {
            outline: none;
            border-color: var(--secondary-color);
            box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
            transform: translateY(-1px);
        }

        .input-group select:hover {
            border-color: var(--secondary-color);
        }

.button-group {
    display: flex;
    gap: 15px;
    margin: 10px 0;
}

.primary-button {
    background: linear-gradient(135deg, var(--secondary-color), #2980b9);
    color: white;
    border: none;
    padding: 14px 30px;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
    letter-spacing: 0.5px;
}

    .primary-button:hover {
        background: linear-gradient(135deg, #2980b9, var(--secondary-color));
        transform: translateY(-2px);
        box-shadow: 0 6px 20px rgba(52, 152, 219, 0.4);
    }

    .primary-button:active {
        transform: translateY(0);
        box-shadow: 0 2px 10px rgba(52, 152, 219, 0.3);
    }

    .primary-button:disabled {
        background: linear-gradient(135deg, #95a5a6, #7f8c8d);
        cursor: not-allowed;
        box-shadow: none;
        transform: none;
    }

    .primary-button:disabled:hover {
        background: linear-gradient(135deg, #95a5a6, #7f8c8d);
        transform: none;
        box-shadow: none;
    }

.nav-buttons {
    display: flex;
    justify-content: space-between;
    margin-top: auto;
    padding: 20px 40px;
    margin-left: -40px;
    margin-right: -40px;
    margin-bottom: -20px;
    background: var(--background-color);
    border-top: 1px solid var(--border-color);
}

.form-section {
    margin-bottom: 30px;
}

.nav-button {
    background: transparent;
    color: var(--secondary-color);
    border: 2px solid var(--secondary-color);
    padding: 12px 28px;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    letter-spacing: 0.5px;
}

    .nav-button:hover {
        background: var(--secondary-color);
        color: white;
        transform: translateY(-2px);
        box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
    }

    .nav-button:active {
        transform: translateY(0);
    }

    .nav-button:disabled {
        background: transparent;
        color: var(--border-color);
        border-color: var(--border-color);
        cursor: not-allowed;
        transform: none;
        box-shadow: none;
    }

    .nav-button:disabled:hover {
        background: transparent;
        color: var(--border-color);
        transform: none;
        box-shadow: none;
    }

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 15px;
        min-height: auto;
    }

    header h1 {
        font-size: 2rem;
    }

    header {
        margin-bottom: 20px;
        padding: 20px 0;
    }

    .tab-buttons {
        flex-wrap: wrap;
    }

    .tab-button {
        flex: 1 1 50%;
        min-width: 120px;
    }

    .tab-panel {
        padding: 25px;
        padding-bottom: 15px;
    }

        .tab-panel h2 {
            font-size: 1.5rem;
        }

    .button-group {
        flex-wrap: wrap;
    }

    .primary-button {
        margin-top: 5px;
    }

    .nav-buttons {
        margin-left: -25px;
        margin-right: -25px;
        margin-bottom: -15px;
        padding: 15px 25px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 10px;
    }

    header {
        margin-bottom: 15px;
        padding: 15px 0;
    }

    header h1 {
        font-size: 1.5rem;
    }

    .tab-button {
        flex: 1 1 100%;
        padding: 15px;
    }

    .tab-panel {
        padding: 20px;
        padding-bottom: 15px;
    }

    .input-group input {
        padding: 12px 14px;
    }

    .primary-button {
        padding: 12px 25px;
        width: 100%;
        margin-top: 8px;
    }

    .button-group {
        flex-direction: column;
        gap: 10px;
    }

    .nav-buttons {
        margin-left: -20px;
        margin-right: -20px;
        margin-bottom: -15px;
        padding: 15px 20px;
    }

    .nav-button {
        padding: 10px 20px;
        font-size: 0.9rem;
    }
}