:root {
    --primary: #4A5568;
    --primary-dark: #2D3748;
    --text: #1A202C;
    --muted: #718096;
    --card: #FFFFFF;
    --background: #F7FAFC;
    --border: #E2E8F0;
    --accent: #4A5568;
    --error: #e74c3c;
    --warning: #ffc107;
}

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

body {
    font-family: 'Inter', 'Segoe UI', system-ui, sans-serif;
    background: var(--background);
    color: var(--text);
    min-height: 100vh;
    overflow-x: hidden;
}

.page-container {
    max-width: 1100px;
    margin: 40px auto;
    background: var(--card);
    padding: 32px;
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
    width: calc(100% - 64px);
}

h1 {
    font-family: 'Merriweather', serif;
    font-weight: 700;
    font-size: 2rem;
    color: var(--text);
    margin-bottom: 8px;
    letter-spacing: -0.5px;
}

.intro {
    font-family: 'Inter', sans-serif;
    font-size: 15px;
    color: var(--muted);
    margin-bottom: 24px;
    line-height: 1.6;
}

.controls {
    display: flex;
    gap: 12px;
    margin-bottom: 30px;
    flex-wrap: wrap;
}

.btn {
    font-family: 'Inter', sans-serif;
    padding: 10px 20px;
    border: 1px solid var(--border);
    border-radius: 6px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    background: white;
    color: var(--text);
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.btn:hover {
    border-color: var(--primary);
    color: var(--primary);
    background: #F7FAFC;
}

.btn-primary {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

.btn-primary:hover {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
    color: white;
}

.semester-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 24px;
    margin-bottom: 20px;
}

.semester-header {
    margin-bottom: 20px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border);
}

.semester-title {
    font-family: 'Merriweather', serif;
    font-size: 1.25rem;
    color: var(--text);
    font-weight: 600;
    letter-spacing: -0.3px;
}

.subjects-table {
    width: 100%;
    border-collapse: collapse;
    margin-bottom: 20px;
}

.subjects-table thead {
    border-bottom: 2px solid var(--border);
}

.subjects-table th {
    font-family: 'Inter', sans-serif;
    text-align: left;
    padding: 12px 8px;
    font-size: 11px;
    letter-spacing: 1.2px;
    color: var(--muted);
    font-weight: 600;
    text-transform: uppercase;
}

.subjects-table td {
    padding: 12px 8px;
    border-bottom: 1px solid var(--border);
}

.subjects-table input,
.subjects-table select {
    font-family: 'Inter', sans-serif;
    width: 100%;
    padding: 8px 12px;
    border: 1px solid var(--border);
    border-radius: 4px;
    font-size: 14px;
    background: white;
    color: var(--text);
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.subjects-table input:focus,
.subjects-table select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(74, 85, 104, 0.1);
}

.subjects-table input::placeholder {
    color: #CBD5E0;
}

.subjects-table tr.invalid select {
    border-color: var(--error);
    background-color: #fff5f5;
}

.invalid-badge {
    background: var(--error);
    color: white;
    padding: 3px 8px;
    border-radius: 4px;
    font-size: 11px;
    font-weight: 600;
    margin-left: 8px;
    letter-spacing: 0.3px;
}

.btn-delete {
    background: transparent;
    border: none;
    color: var(--muted);
    cursor: pointer;
    font-size: 1.25rem;
    padding: 4px 8px;
    transition: color 0.2s;
}

.btn-delete:hover {
    color: var(--error);
}

.semester-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 16px;
}

.semester-footer-info {
    font-family: 'Roboto Mono', monospace;
    font-size: 13px;
    color: var(--muted);
}

.semester-footer-buttons {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.results-section {
    margin-top: 40px;
    padding-top: 40px;
    border-top: 1px solid var(--border);
}

.results-section h2 {
    font-family: 'Merriweather', serif;
    font-size: 1.75rem;
    color: var(--text);
    margin-bottom: 24px;
    letter-spacing: -0.5px;
}

.error-banner {
    background: #fff5f5;
    border: 2px solid var(--error);
    border-left: 3px solid var(--error);
    border-radius: 6px;
    padding: 16px;
    margin-bottom: 24px;
    display: flex;
    align-items: flex-start;
    gap: 12px;
    color: #c0392b;
    font-size: 14px;
    line-height: 1.6;
}

.error-banner svg {
    flex-shrink: 0;
    margin-top: 2px;
}

.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 24px;
}

.result-card {
    background: var(--background);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 24px;
    text-align: center;
}

.result-card h3 {
    font-family: 'Inter', sans-serif;
    font-size: 12px;
    letter-spacing: 1.2px;
    color: var(--muted);
    font-weight: 600;
    text-transform: uppercase;
    margin-bottom: 16px;
}

.circular-gauge {
    position: relative;
    width: 140px;
    height: 140px;
    margin: 0 auto 12px;
}

.gauge-svg {
    transform: rotate(-90deg);
    width: 100%;
    height: 100%;
}

.gauge-bg {
    fill: none;
    stroke: var(--border);
    stroke-width: 10;
}

.gauge-progress {
    fill: none;
    stroke: var(--primary);
    stroke-width: 10;
    stroke-linecap: round;
    transition: stroke-dashoffset 0.6s ease;
}

.gauge-value {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
}

.gauge-number {
    font-family: 'Roboto Mono', monospace;
    font-size: 2rem;
    font-weight: 500;
    line-height: 1;
    margin-bottom: 4px;
    color: var(--primary);
    letter-spacing: -1px;
}

.gauge-label {
    font-family: 'Inter', sans-serif;
    font-size: 11px;
    color: var(--muted);
}

.result-card .credits {
    font-family: 'Inter', sans-serif;
    color: var(--muted);
    margin-top: 8px;
    font-size: 13px;
}

.cgpa-result {
    grid-column: 1 / -1;
    border: 2px solid var(--primary);
    background: white;
}

.grading-modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    padding: 20px;
    overflow-y: auto;
}

.grading-modal.active {
    display: flex;
    align-items: center;
    justify-content: center;
}

.grading-content {
    background: white;
    border-radius: 8px;
    padding: 32px;
    max-width: 600px;
    width: 100%;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.grading-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 24px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border);
}

.grading-header h2 {
    font-family: 'Merriweather', serif;
    font-size: 1.5rem;
    color: var(--text);
    letter-spacing: -0.3px;
}

.close-btn {
    background: transparent;
    border: none;
    font-size: 1.5rem;
    color: var(--muted);
    cursor: pointer;
    padding: 0;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color 0.2s;
}

.close-btn:hover {
    color: var(--text);
}

.modal-description {
    font-family: 'Inter', sans-serif;
    color: var(--muted);
    margin-bottom: 24px;
    line-height: 1.6;
    font-size: 14px;
}

.grade-row {
    display: grid;
    grid-template-columns: 1fr 1fr auto;
    gap: 12px;
    margin-bottom: 12px;
    align-items: center;
}

.grade-row input {
    font-family: 'Inter', sans-serif;
    padding: 8px 12px;
    border: 1px solid var(--border);
    border-radius: 4px;
    font-size: 14px;
}

.grade-row input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(74, 85, 104, 0.1);
}

.grade-labels {
    display: grid;
    grid-template-columns: 1fr 1fr auto;
    gap: 12px;
    margin-bottom: 12px;
}

.grade-label {
    font-family: 'Inter', sans-serif;
    font-size: 11px;
    font-weight: 600;
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.preset-section {
    margin-bottom: 24px;
    padding: 16px;
    background: var(--background);
    border-radius: 6px;
    border: 1px solid var(--border);
}

.preset-section label {
    font-family: 'Inter', sans-serif;
    display: block;
    font-weight: 600;
    color: var(--text);
    margin-bottom: 8px;
    font-size: 14px;
}

.preset-section select {
    font-family: 'Inter', sans-serif;
    width: 100%;
    padding: 8px 12px;
    border: 1px solid var(--border);
    border-radius: 4px;
    font-size: 14px;
    background: white;
    color: var(--text);
    cursor: pointer;
}

.preset-section select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(74, 85, 104, 0.1);
}

.preset-note {
    font-family: 'Inter', sans-serif;
    color: var(--muted);
    font-size: 13px;
    margin-top: 6px;
    line-height: 1.5;
}

.preset-disclaimer {
    background: #fff3cd;
    border: 2px solid var(--warning);
    border-left: 3px solid var(--warning);
    border-radius: 6px;
    padding: 12px;
    margin-bottom: 20px;
    color: #856404;
    font-size: 13px;
    line-height: 1.5;
    display: none;
}

.preset-disclaimer.active {
    display: block;
}

.preset-disclaimer strong {
    display: block;
    margin-bottom: 4px;
}

@media (max-width: 768px) {
    .page-container {
        margin: 20px auto;
        padding: 20px;
        width: calc(100% - 40px);
    }

    h1 {
        font-size: 1.5rem;
    }

    .intro {
        font-size: 14px;
    }

    .semester-card {
        padding: 16px;
    }

    .subjects-table {
        display: block;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
    }

    .subjects-table table {
        min-width: 600px;
    }

    .semester-footer {
        flex-direction: column;
        align-items: flex-start;
        gap: 12px;
    }

    .semester-footer-buttons {
        width: 100%;
    }

    .semester-footer-buttons .btn {
        flex: 1;
        justify-content: center;
    }

    .circular-gauge {
        width: 120px;
        height: 120px;
    }

    .gauge-number {
        font-size: 1.75rem;
    }

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

    .controls {
        flex-direction: column;
    }

    .controls .btn {
        width: 100%;
        justify-content: center;
    }

    .grading-content {
        padding: 24px;
    }
}

@media (max-width: 480px) {
    .page-container {
        padding: 16px;
        width: calc(100% - 32px);
    }

    h1 {
        font-size: 1.3rem;
    }

    .results-section h2 {
        font-size: 1.4rem;
    }

    .circular-gauge {
        width: 100px;
        height: 100px;
    }

    .gauge-number {
        font-size: 1.5rem;
    }
}