:root {
    --bg-dark: #0f172a;
    --bg-glass: rgba(30, 41, 59, 0.7);
    --border-glass: rgba(255, 255, 255, 0.1);
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --primary: #8b5cf6;
    --primary-hover: #7c3aed;
    --gradient-1: #c084fc;
    --gradient-2: #8b5cf6;
    --gradient-3: #3b82f6;
    --danger: #ef4444;
    --danger-hover: #dc2626;
    --input-bg: rgba(15, 23, 42, 0.6);
    --input-border: rgba(255, 255, 255, 0.2);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Outfit', sans-serif;
}

body {
    background-color: var(--bg-dark);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding: 3rem 1rem;
    overflow-x: hidden;
    position: relative;
}

/* Background Blobs for Visual Aesthetics */
.background-animation {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: -1;
    overflow: hidden;
}

.blob {
    position: absolute;
    border-radius: 50%;
    filter: blur(100px);
    opacity: 0.6;
    animation: float 20s infinite ease-in-out alternate;
}

.blob-1 {
    width: 400px;
    height: 400px;
    background: var(--gradient-2);
    top: -100px;
    left: -100px;
}

.blob-2 {
    width: 500px;
    height: 500px;
    background: var(--gradient-3);
    bottom: -150px;
    right: -100px;
    animation-delay: -10s;
}

@keyframes float {
    0% { transform: translate(0, 0) scale(1); }
    100% { transform: translate(50px, 50px) scale(1.2); }
}

.container {
    width: 100%;
    max-width: 800px;
    z-index: 10;
}

header {
    text-align: center;
    margin-bottom: 2rem;
}

header h1 {
    font-size: 3rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--gradient-1), var(--gradient-3));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 0.5rem;
}

header p {
    color: var(--text-muted);
    font-size: 1.1rem;
    font-weight: 300;
    margin-bottom: 1rem;
}

.glass-card-link {
    position: absolute;
    top: 2rem;
    right: 2rem;
    background: var(--bg-glass);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--border-glass);
    padding: 0.8rem 1.2rem;
    border-radius: 16px;
    color: var(--text-main);
    text-decoration: none;
    font-weight: 600;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.3);
    transition: all 0.3s ease;
    z-index: 50;
}

.glass-card-link:hover {
    transform: translateY(-3px);
    border-color: var(--primary);
    box-shadow: 0 15px 30px -5px rgba(139, 92, 246, 0.4);
}

/* Glassmorphism Panels */
.glass-panel {
    background: var(--bg-glass);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--border-glass);
    border-radius: 24px;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    padding: 2rem;
    margin-bottom: 2rem;
}

/* Calculator Table Area */
.table-header {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 40px;
    gap: 1rem;
    padding-bottom: 1rem;
    margin-bottom: 1rem;
    border-bottom: 1px solid var(--border-glass);
    color: var(--text-muted);
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 600;
}

.course-row {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 40px;
    gap: 1rem;
    margin-bottom: 1rem;
    align-items: center;
    animation: slideIn 0.3s ease-out forwards;
}

@keyframes slideIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.course-row.removing {
    animation: fadeOut 0.3s ease-in forwards;
}

@keyframes fadeOut {
    from { opacity: 1; transform: scale(1); }
    to { opacity: 0; transform: scale(0.9); }
}

/* Inputs */
input {
    width: 100%;
    background: var(--input-bg);
    border: 1px solid var(--input-border);
    color: var(--text-main);
    padding: 0.75rem 1rem;
    border-radius: 12px;
    font-size: 1rem;
    outline: none;
    transition: all 0.2s ease;
}

input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(139, 92, 246, 0.25);
}

input::placeholder {
    color: rgba(148, 163, 184, 0.5);
}

/* Range Slider Styling */
.slider-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    background: var(--input-bg);
    border: 1px solid var(--input-border);
    border-radius: 12px;
    padding: 0.5rem 1rem;
    height: 100%;
}

.course-slider {
    -webkit-appearance: none;
    width: 100%;
    height: 6px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 5px;
    outline: none;
    padding: 0;
    border: none;
}

.course-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--gradient-1);
    cursor: pointer;
    box-shadow: 0 0 10px var(--gradient-2);
    transition: transform 0.1s ease;
}

.course-slider::-webkit-slider-thumb:hover {
    transform: scale(1.2);
}

.course-slider::-moz-range-thumb {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--gradient-1);
    cursor: pointer;
    box-shadow: 0 0 10px var(--gradient-2);
    border: none;
    transition: transform 0.1s ease;
}

.course-slider::-moz-range-thumb:hover {
    transform: scale(1.2);
}

.slider-display {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--gradient-1);
    letter-spacing: 1px;
}

/* Buttons */
.btn-primary {
    background: linear-gradient(135deg, var(--gradient-2), var(--gradient-3));
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.3s ease;
    width: 100%;
    justify-content: center;
    margin-top: 1rem;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 20px -10px var(--gradient-2);
}

.btn-icon {
    background: transparent;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
}

.btn-icon:hover {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger);
}

/* Results Area */
.result-card {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 2.5rem;
    position: sticky;
    bottom: 2rem;
}

.highlight-panel {
    background: linear-gradient(135deg, rgba(139, 92, 246, 0.1), rgba(59, 130, 246, 0.1));
    border: 1px solid rgba(139, 92, 246, 0.3);
}

.result-group {
    display: flex;
    flex-direction: column;
}

.result-label {
    font-size: 0.9rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.25rem;
}

.result-value {
    font-size: 1.5rem;
    font-weight: 600;
}

.result-divider {
    width: 1px;
    height: 40px;
    background: var(--border-glass);
}

.cgpa-group {
    align-items: flex-end;
}

.cgpa-value {
    font-size: 3rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--gradient-1), var(--gradient-3));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    line-height: 1;
    transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.cgpa-value.pop {
    transform: scale(1.1);
}

/* Share Button */
.share-btn {
    margin-top: 1.5rem;
    background: linear-gradient(135deg, #10b981, #059669);
    box-shadow: 0 10px 25px -5px rgba(16, 185, 129, 0.4);
}

.share-btn:hover {
    box-shadow: 0 15px 30px -5px rgba(16, 185, 129, 0.6);
}

/* Responsive */
@media (max-width: 640px) {
    header h1 { font-size: 2.2rem; }
    
    .table-header { display: none; }
    
    .course-row {
        grid-template-columns: 1fr 1fr;
        grid-template-areas: 
            "course course"
            "credits grade"
            "action action";
        background: rgba(0,0,0,0.2);
        padding: 1rem;
        border-radius: 12px;
        position: relative;
    }
    
    .course-row input:first-child { grid-area: course; }
    .course-row input[type="number"] { grid-area: credits; }
    .course-row select { grid-area: grade; }
    
    .course-row .btn-icon {
        position: absolute;
        top: 0.5rem;
        right: 0.5rem;
        grid-area: auto;
    }
    
    .result-card {
        flex-direction: column;
        gap: 1.5rem;
        align-items: center;
        text-align: center;
    }
    
    .result-divider {
        width: 100%;
        height: 1px;
    }
    
    .cgpa-group {
        align-items: center;
    }

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

    .glass-card-link {
        position: relative;
        top: 0;
        right: 0;
        margin: 1rem auto;
        justify-content: center;
        max-width: 300px;
    }

    .grade-legend {
        position: relative;
        top: 0;
        left: 0;
        margin: 1rem auto;
        max-width: 300px;
    }

    /* Mobile check: larger thumb for touch targets */
    .course-slider::-webkit-slider-thumb {
        width: 28px;
        height: 28px;
    }
    
    .course-slider::-moz-range-thumb {
        width: 28px;
        height: 28px;
    }

    /* Adjust padding to prevent cramped layout on 375px screens */
    .glass-panel {
        padding: 1.5rem;
    }
    .result-card {
        padding: 1.5rem;
    }
}

/* Simulator Styles */
#grade-simulator {
    margin-top: 5rem;
}

.simulator-header {
    text-align: center;
    margin-bottom: 2rem;
}

.simulator-header h2 {
    font-size: 2rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--gradient-1), var(--gradient-3));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 0.5rem;
}

.simulator-header p {
    color: var(--text-muted);
    font-size: 1rem;
    font-weight: 300;
}

.simulator-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.simulator-input-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.simulator-input-group label {
    font-size: 0.9rem;
    color: var(--text-muted);
    font-weight: 600;
}

.sim-slider-wrapper {
    flex-direction: row;
    justify-content: space-between;
}

.sim-number-input {
    width: 80px;
    padding: 0.5rem;
    text-align: center;
}

.simulator-result {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-glass);
}

.sim-result-value {
    font-size: 2.5rem;
    font-weight: 800;
    margin-top: 0.5rem;
    background: linear-gradient(135deg, var(--gradient-1), var(--gradient-3));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.sim-result-value.impossible {
    background: linear-gradient(135deg, #ef4444, #f97316);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

/* Guide Styles */
.explanation-card {
    margin-bottom: 1.5rem;
}

/* Legend Styles */
.grade-legend {
    position: absolute;
    top: 2rem;
    left: 2rem;
    margin: 0;
    max-width: 300px;
    background: var(--bg-glass);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--border-glass);
    border-radius: 12px;
    padding: 0.5rem 1rem;
    text-align: left;
    font-size: 0.9rem;
    z-index: 50;
}

.grade-legend summary {
    cursor: pointer;
    font-weight: 600;
    color: var(--gradient-1);
    outline: none;
    list-style: none; /* Hide default arrow */
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.grade-legend summary::after {
    content: "▼";
    font-size: 0.8rem;
    transition: transform 0.2s ease;
}

.grade-legend[open] summary::after {
    transform: rotate(180deg);
}

.grade-legend summary::-webkit-details-marker {
    display: none;
}

.legend-content {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-glass);
}

.legend-content span {
    background: rgba(255, 255, 255, 0.1);
    padding: 0.2rem 0.6rem;
    border-radius: 6px;
    font-weight: 600;
    color: var(--text-main);
}

.guide-card {
    margin-top: 5rem;
}

.guide-content {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.guide-step {
    display: flex;
    gap: 1rem;
    align-items: flex-start;
    background: rgba(0, 0, 0, 0.2);
    padding: 1.5rem;
    border-radius: 16px;
    border: 1px solid var(--border-glass);
    transition: transform 0.2s ease;
}

.guide-step:hover {
    transform: translateX(10px);
    background: rgba(255, 255, 255, 0.05);
}

.step-number {
    background: linear-gradient(135deg, var(--gradient-1), var(--gradient-3));
    color: white;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    font-weight: 800;
    flex-shrink: 0;
    box-shadow: 0 5px 15px -5px var(--gradient-2);
}

.step-text h3 {
    margin-bottom: 0.5rem;
    color: var(--text-main);
    font-size: 1.1rem;
}

.step-text p {
    color: var(--text-muted);
    font-size: 0.95rem;
    line-height: 1.5;
}