:root {
    /* Master Brand Colors (WCAG AA Compliant) */
    --primary: #0052CC;
    --primary-dark: #003A99;
    --primary-brand: #0052CC;
    --secondary: #003A99;
    --accent: #1B8917;
    --success: #1B8917;
    --error: #AE0A07;
    --warning: #A85C00;
    --bg: #f5f5f5;
    --card-bg: #ffffff;
    --text: #172B4D;
    --text-light: #172B4D;
    --border: #e0e0e0;
    --shadow: 0 2px 8px rgba(0,0,0,0.1);
}

body.dark-mode {
    --bg: #1a1a2e;
    --card-bg: #2d2d3d;
    --text: #e0e0e0;
    --text-light: #999;
    --border: #444;
    --shadow: 0 2px 8px rgba(0,0,0,0.3);
}

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

html, body {
    height: 100%;
    width: 100%;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg);
    color: var(--text);
    transition: all 0.3s ease;
    line-height: 1.6;
}

.navbar {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 0;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.logo {
    font-size: 1.8rem;
    font-weight: bold;
}

.nav-buttons {
    display: flex;
    gap: 1rem;
}

.nav-btn {
    background: rgba(255,255,255,0.2);
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.3s;
}

.nav-btn:hover {
    background: rgba(255,255,255,0.3);
    transform: translateY(-2px);
}

.container {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 1rem;
}

.content-wrapper {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}

.back-btn, .export-btn {
    background: var(--primary);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
    transition: all 0.3s;
}

.back-btn:hover, .export-btn:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.back-btn {
    display: none;
}

.export-btn {
    display: none;
}

.header {
    text-align: center;
    margin-bottom: 3rem;
}

.header h1 {
    font-size: 2.5rem;
    color: var(--primary);
    margin-bottom: 0.5rem;
}

.header p {
    font-size: 1.1rem;
    color: var(--text-light);
}

.calculator-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.calc-card {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 2rem;
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.3s;
    text-align: center;
    box-shadow: var(--shadow);
}

.calc-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 8px 20px rgba(0,0,0,0.2);
}

.calc-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.calc-card h3 {
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
}

.calc-card p {
    font-size: 0.95rem;
    opacity: 0.9;
}

.form-container {
    max-width: 600px;
    margin: 0 auto;
}

.form-container h2 {
    color: var(--primary);
    margin-bottom: 1.5rem;
    font-size: 1.8rem;
}

.form-container form {
    display: flex;
    flex-direction: column;
    gap: 1.2rem;
}

.form-container label {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    font-weight: 500;
}

.form-container input,
.form-container select {
    padding: 0.8rem;
    border: 2px solid var(--border);
    border-radius: 6px;
    background: var(--card-bg);
    color: var(--text);
    font-size: 1rem;
    transition: border-color 0.3s;
}

.form-container input:focus,
.form-container select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(255, 107, 107, 0.1);
}

.form-container button[type="submit"] {
    background: var(--primary);
    color: white;
    border: none;
    padding: 1rem;
    border-radius: 6px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    margin-top: 1rem;
}

.form-container button[type="submit"]:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(255, 107, 107, 0.3);
}

.results-container {
    background: var(--bg);
    padding: 2rem;
    border-radius: 12px;
    margin-top: 1.5rem;
}

.results-container h2 {
    color: var(--primary);
    margin-bottom: 1.5rem;
    font-size: 1.6rem;
}

.result-item {
    background: var(--card-bg);
    padding: 1rem;
    margin-bottom: 1rem;
    border-left: 4px solid var(--primary);
    border-radius: 6px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.result-item strong {
    color: var(--primary);
}

.logic-section {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 12px;
    margin-top: 2rem;
    border: 2px solid var(--primary);
}

.logic-section h3 {
    color: var(--primary);
    margin-bottom: 1rem;
}

.logic-section ol {
    margin-left: 1.5rem;
}

.logic-section li {
    margin-bottom: 0.5rem;
    color: var(--text-light);
}

.history-container {
    max-width: 600px;
    margin: 0 auto;
}

.history-container h2 {
    color: var(--primary);
    margin-bottom: 1.5rem;
}

.history-item {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 1rem 1.5rem;
    margin-bottom: 0.8rem;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.3s;
}

.history-item:hover {
    transform: translateX(5px);
    box-shadow: var(--shadow);
}

.ad-container {
    background: var(--card-bg);
    padding: 1rem;
    border-radius: 12px;
    margin: 2rem 0;
    box-shadow: var(--shadow);
    min-height: 250px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-light);
}

.footer {
    background: var(--primary);
    color: white;
    text-align: center;
    padding: 2rem;
    margin-top: 3rem;
}

.footer p {
    margin: 0.5rem 0;
    font-size: 0.9rem;
}

@media (max-width: 768px) {
    .nav-container {
        flex-direction: column;
        gap: 1rem;
        padding: 1rem;
    }

    .nav-buttons {
        width: 100%;
        justify-content: space-around;
    }

    .calculator-grid {
        grid-template-columns: 1fr;
    }

    .content-wrapper {
        padding: 1.5rem 1rem;
    }

    .header h1 {
        font-size: 1.8rem;
    }

    .result-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }

    .logo {
        font-size: 1.4rem;
    }
}

@media (max-width: 480px) {
    .header h1 {
        font-size: 1.4rem;
    }

    .nav-btn {
        padding: 0.4rem 0.8rem;
        font-size: 0.8rem;
    }

    .container {
        margin: 1rem auto;
        padding: 0 0.5rem;
    }

    .calc-icon {
        font-size: 2rem;
    }
}