/* ===== CSS Variables & Reset ===== */
:root {
    /* Color Palette */
    --primary-hue: 250;
    --primary: hsl(var(--primary-hue), 85%, 60%);
    --primary-light: hsl(var(--primary-hue), 85%, 70%);
    --primary-dark: hsl(var(--primary-hue), 85%, 45%);
    --primary-glow: hsla(var(--primary-hue), 85%, 60%, 0.4);

    --accent-hue: 170;
    --accent: hsl(var(--accent-hue), 75%, 50%);
    --accent-light: hsl(var(--accent-hue), 75%, 65%);

    --success: hsl(145, 70%, 50%);
    --success-light: hsl(145, 70%, 65%);
    --warning: hsl(40, 90%, 55%);
    --danger: hsl(0, 75%, 60%);

    /* Background Colors */
    --bg-dark: hsl(230, 25%, 8%);
    --bg-card: hsla(230, 20%, 15%, 0.6);
    --bg-card-hover: hsla(230, 20%, 18%, 0.8);

    /* Text Colors */
    --text-primary: hsl(0, 0%, 95%);
    --text-secondary: hsl(230, 15%, 70%);
    --text-muted: hsl(230, 15%, 50%);

    /* Borders */
    --border-subtle: hsla(230, 20%, 40%, 0.3);
    --border-glow: hsla(var(--primary-hue), 85%, 60%, 0.3);

    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;

    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --radius-full: 9999px;

    /* Shadows */
    --shadow-sm: 0 2px 8px hsla(0, 0%, 0%, 0.2);
    --shadow-md: 0 4px 20px hsla(0, 0%, 0%, 0.3);
    --shadow-lg: 0 8px 40px hsla(0, 0%, 0%, 0.4);
    --shadow-glow: 0 0 30px var(--primary-glow);

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 400ms ease;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-dark);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
    overflow-x: hidden;
}

/* Background Gradient Animation */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background:
        radial-gradient(ellipse at 20% 20%, hsla(var(--primary-hue), 70%, 40%, 0.15) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 80%, hsla(var(--accent-hue), 70%, 40%, 0.1) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 50%, hsla(280, 60%, 30%, 0.08) 0%, transparent 60%);
    pointer-events: none;
    z-index: 0;
    animation: bgPulse 10s ease-in-out infinite;
}

@keyframes bgPulse {

    0%,
    100% {
        opacity: 1;
    }

    50% {
        opacity: 0.7;
    }
}

/* ===== App Container ===== */
.app-container {
    position: relative;
    z-index: 1;
    max-width: 800px;
    margin: 0 auto;
    padding: var(--space-lg);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ===== Header ===== */
.header {
    text-align: center;
    padding: var(--space-xl) 0 var(--space-2xl);
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    margin-bottom: var(--space-sm);
}

.logo-icon {
    width: 48px;
    height: 48px;
}

.logo-text {
    font-size: 2rem;
    font-weight: 800;
    letter-spacing: -0.02em;
}

.logo-text .accent {
    background: linear-gradient(135deg, var(--primary-light), var(--accent));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.header-subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
    font-weight: 400;
}

/* ===== Main Content ===== */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
}

/* ===== Glass Card ===== */
.card {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    padding: var(--space-xl);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    transition: all var(--transition-base);
}

.card:hover {
    background: var(--bg-card-hover);
    border-color: var(--border-glow);
    box-shadow: var(--shadow-md);
}

.card-header {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    margin-bottom: var(--space-lg);
}

.card-icon {
    width: 40px;
    height: 40px;
    flex-shrink: 0;
}

.card-header h2 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* ===== Input Styles ===== */
.input-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-lg);
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: var(--space-xs);
}

.input-group label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.input-group input,
.input-group select {
    padding: var(--space-md);
    background: hsla(230, 20%, 10%, 0.6);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1rem;
    font-family: inherit;
    transition: all var(--transition-fast);
}

/* Hide number input spinners */
input[type=number]::-webkit-inner-spin-button,
input[type=number]::-webkit-outer-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

input[type=number] {
    -moz-appearance: textfield;
    appearance: none;
}

.input-group input::placeholder {
    color: var(--text-muted);
}

.input-group input:focus,
.input-group select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-glow);
}

.input-group select {
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='20' height='20' viewBox='0 0 24 24' fill='none' stroke='%23888' stroke-width='2'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 40px;
}

.input-group select option {
    background: var(--bg-dark);
    color: var(--text-primary);
}

.input-hint {
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* ===== Add Course Form ===== */
.add-course-form {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}

.form-row {
    display: flex;
    gap: var(--space-md);
    flex-wrap: wrap;
}

.flex-1 {
    flex: 1;
    min-width: 100px;
}

.flex-2 {
    flex: 2;
    min-width: 200px;
}

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: var(--space-md) var(--space-xl);
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    font-family: inherit;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
    box-shadow: var(--shadow-sm), 0 0 20px var(--primary-glow);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md), 0 0 30px var(--primary-glow);
}

.btn-primary:active {
    transform: translateY(0);
}

.add-btn {
    align-self: flex-start;
}

/* ===== Course List ===== */
.course-list {
    margin-top: var(--space-lg);
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: var(--space-xl);
    color: var(--text-muted);
    text-align: center;
}

.empty-animation {
    width: 120px;
    height: 120px;
    margin-bottom: var(--space-md);
}

.empty-state p {
    font-weight: 500;
    color: var(--text-secondary);
}

.empty-state span {
    font-size: 0.875rem;
}

/* Course Item */
.course-item {
    display: flex;
    align-items: center;
    padding: var(--space-md) var(--space-lg);
    background: hsla(230, 20%, 12%, 0.8);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    gap: var(--space-md);
    animation: slideIn 0.3s ease forwards;
}

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

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

.course-info {
    flex: 1;
}

.course-name {
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 2px;
}

.course-details {
    font-size: 0.875rem;
    color: var(--text-muted);
}

.course-grade {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    background: linear-gradient(135deg, var(--primary), var(--accent));
    border-radius: var(--radius-sm);
    font-weight: 700;
    font-size: 1.1rem;
    color: white;
}

.course-grade.grade-10 {
    background: linear-gradient(135deg, var(--success), var(--accent));
}

.course-grade.grade-9 {
    background: linear-gradient(135deg, hsl(160, 70%, 45%), var(--accent));
}

.course-grade.grade-8 {
    background: linear-gradient(135deg, var(--primary), var(--accent));
}

.course-grade.grade-7 {
    background: linear-gradient(135deg, hsl(220, 70%, 55%), var(--primary));
}

.course-grade.grade-6 {
    background: linear-gradient(135deg, hsl(45, 80%, 50%), hsl(30, 80%, 50%));
}

.course-grade.grade-5 {
    background: linear-gradient(135deg, var(--warning), hsl(20, 80%, 50%));
}

.course-grade.grade-4 {
    background: linear-gradient(135deg, hsl(15, 70%, 50%), var(--danger));
}

.course-grade.grade-0 {
    background: linear-gradient(135deg, var(--danger), hsl(350, 70%, 40%));
}

.delete-btn {
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: transparent;
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
    color: var(--text-muted);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.delete-btn:hover {
    background: hsla(0, 70%, 50%, 0.2);
    border-color: var(--danger);
    color: var(--danger);
}

/* ===== Results Card ===== */
.results-card {
    background: linear-gradient(135deg, hsla(var(--primary-hue), 30%, 15%, 0.8), hsla(var(--accent-hue), 30%, 12%, 0.8));
    border: 1px solid hsla(var(--primary-hue), 50%, 40%, 0.3);
}

.results-grid {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: var(--space-lg);
    align-items: center;
}

.result-item {
    text-align: center;
    padding: var(--space-lg);
}

.result-label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: var(--space-sm);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.result-value {
    font-size: 3rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--text-primary), var(--primary-light));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1.2;
    transition: all var(--transition-base);
}

.result-bar {
    height: 6px;
    background: hsla(230, 20%, 30%, 0.5);
    border-radius: var(--radius-full);
    margin: var(--space-md) 0 var(--space-sm);
    overflow: hidden;
}

.result-bar-fill {
    height: 100%;
    width: 0%;
    background: linear-gradient(90deg, var(--primary), var(--accent));
    border-radius: var(--radius-full);
    transition: width 0.8s cubic-bezier(0.4, 0, 0.2, 1);
}

.result-credits {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.result-divider {
    width: 1px;
    height: 80px;
    background: linear-gradient(to bottom, transparent, var(--border-subtle), transparent);
}

.cgpa-change {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    margin-top: var(--space-lg);
    padding: var(--space-md);
    background: hsla(230, 20%, 20%, 0.5);
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.change-icon {
    font-size: 1.2rem;
    transition: transform var(--transition-fast);
}

.cgpa-change.positive .change-icon {
    color: var(--success);
}

.cgpa-change.negative .change-icon {
    color: var(--danger);
}

.cgpa-change.positive .change-text {
    color: var(--success-light);
}

.cgpa-change.negative .change-text {
    color: var(--danger);
}

/* ===== Grade Reference ===== */
.grade-reference {
    padding: var(--space-lg);
}

.grade-reference .card-header {
    margin-bottom: 0;
    cursor: pointer;
    padding: var(--space-sm);
    margin: calc(var(--space-sm) * -1);
    border-radius: var(--radius-sm);
    transition: background var(--transition-fast);
}

.grade-reference .card-header:hover {
    background: hsla(230, 20%, 25%, 0.5);
}

.grade-reference .card-header h3 {
    flex: 1;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.chevron {
    transition: transform var(--transition-base);
}

.card-header.collapsed .chevron {
    transform: rotate(0deg);
}

.card-header:not(.collapsed) .chevron {
    transform: rotate(180deg);
}

.grade-table-wrapper {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-slow), margin var(--transition-slow);
}

.grade-table-wrapper.expanded {
    max-height: 400px;
    margin-top: var(--space-lg);
}

.grade-table {
    width: 100%;
    border-collapse: collapse;
}

.grade-table th,
.grade-table td {
    padding: var(--space-sm) var(--space-md);
    text-align: left;
    border-bottom: 1px solid var(--border-subtle);
}

.grade-table th {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.grade-table td {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.grade-table td:first-child {
    font-weight: 600;
    color: var(--text-primary);
}

.grade-table tbody tr:last-child td {
    border-bottom: none;
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    padding: var(--space-xl) 0 var(--space-lg);
    color: var(--text-muted);
    font-size: 0.875rem;
}

.footer-note {
    margin-top: var(--space-xs);
    font-size: 0.75rem;
}

/* ===== Success Overlay ===== */
.success-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    background: hsla(0, 0%, 0%, 0.5);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
    z-index: 1000;
    pointer-events: none;
}

.success-overlay.show {
    opacity: 1;
    visibility: visible;
}

.success-animation {
    width: 200px;
    height: 200px;
}

/* ===== Responsive Design ===== */
@media (max-width: 640px) {
    .app-container {
        padding: var(--space-md);
    }

    .card {
        padding: var(--space-lg);
    }

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

    .form-row {
        flex-direction: column;
    }

    .flex-1,
    .flex-2 {
        min-width: 100%;
    }

    .add-btn {
        width: 100%;
    }

    .results-grid {
        grid-template-columns: 1fr;
        gap: var(--space-md);
    }

    .result-divider {
        width: 80%;
        height: 1px;
        margin: 0 auto;
    }

    .result-value {
        font-size: 2.5rem;
    }

    .logo-text {
        font-size: 1.5rem;
    }
}

/* ===== Utility Animations ===== */
@keyframes pulse {

    0%,
    100% {
        transform: scale(1);
    }

    50% {
        transform: scale(1.05);
    }
}

.pulse {
    animation: pulse 0.5s ease;
}

@keyframes shake {

    0%,
    100% {
        transform: translateX(0);
    }

    25% {
        transform: translateX(-5px);
    }

    75% {
        transform: translateX(5px);
    }
}

.shake {
    animation: shake 0.3s ease;
}