:root {
    --primary: #4f46e5;
    --primary-dark: #4338ca;
    --secondary: #ec4899;
    --bg-body: #f3f4f6;
    --bg-card: #ffffff;
    --text-main: #1f2937;
    --text-muted: #6b7280;
    --border: #e5e7eb;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --radius: 12px;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

* {
    box-sizing: border_box;
    margin: 0;
    padding: 0;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

body {
    background-color: var(--bg-body);
    color: var(--text-main);
    line-height: 1.5;
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
}

h1,
h2,
h3,
h4 {
    color: var(--text-main);
    font-weight: 700;
}

a {
    text-decoration: none;
    color: var(--primary);
    transition: color 0.2s;
}

/* Utilities */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

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

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 20px;
    border-radius: 8px;
    font-weight: 500;
    cursor: pointer;
    border: none;
    transition: all 0.2s;
    font-size: 0.95rem;
}

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

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

.btn-secondary {
    background: white;
    border: 1px solid var(--border);
    color: var(--text-main);
}

.btn-secondary:hover {
    background: #f9fafb;
    border-color: #d1d5db;
}

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

.btn-full {
    width: 100%;
}

.form-group {
    margin-bottom: 16px;
}

.form-label {
    display: block;
    margin-bottom: 6px;
    font-weight: 500;
    color: var(--text-main);
    font-size: 0.9em;
}

.form-control {
    width: 100%;
    padding: 10px 14px;
    border-radius: 8px;
    border: 1px solid var(--border);
    font-size: 1rem;
    transition: border-color 0.2s;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

/* Mobile-First Grid System */
.grid {
    display: grid;
    gap: 20px;
}

@media (min-width: 768px) {
    .grid-2 {
        grid-template-columns: repeat(2, 1fr);
    }

    .grid-3 {
        grid-template-columns: repeat(3, 1fr);
    }

    .grid-4 {
        grid-template-columns: repeat(4, 1fr);
    }
}

/* Header */
.navbar {
    background: var(--bg-card);
    padding: 16px 20px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-brand {
    font-weight: 800;
    font-size: 1.25rem;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: 8px;
}

.nav-links {
    display: flex;
    gap: 20px;
}

/* Dashboard Stats */
.stat-card {
    display: flex;
    flex-direction: column;
}

.stat-value {
    font-size: 2rem;
    font-weight: 800;
    color: var(--primary);
}

.stat-label {
    color: var(--text-muted);
}

/* Marks Entry Table (Mobile Optimized) */
.marks-entry-list {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.student-mark-row {
    background: var(--bg-card);
    padding: 16px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
}

.student-info {
    flex: 1;
}

.student-name {
    font-weight: 600;
    font-size: 1.05rem;
}

.student-roll {
    font-size: 0.85rem;
    color: var(--text-muted);
}

.mark-input-group {
    width: 100px;
    flex-shrink: 0;
}

.mark-input {
    text-align: center;
    font-weight: 700;
    font-size: 1.2rem;
}

/* Tables for Desktop */
.table-container {
    overflow-x: auto;
}

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

th,
td {
    padding: 12px;
    text-align: left;
    border-bottom: 1px solid var(--border);
}

th {
    background: #f9fafb;
    font-weight: 600;
    color: var(--text-muted);
}

/* Login */
.login-page {
    display: flex;
    min-height: 100vh;
    align-items: center;
    justify-content: center;
    padding: 16px;
    background: linear-gradient(135deg, #f3f4f6 0%, #e0e7ff 100%);
}

.login-card {
    width: 100%;
    max-width: 380px;
    background: white;
    padding: 24px;
    border-radius: 16px;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.1);
}

@media (min-width: 768px) {
    .login-card {
        padding: 40px;
        border-radius: 20px;
    }
}

.logo-placeholder {
    width: 60px;
    height: 60px;
    background: var(--primary);
    border-radius: 12px;
    margin: 0 auto 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 24px;
}

/* Alert/Flash */
.alert {
    padding: 12px 16px;
    border-radius: 8px;
    margin-bottom: 20px;
    font-weight: 500;
}

.alert-success {
    background: #d1fae5;
    color: #065f46;
}

.alert-error {
    background: #fee2e2;
    color: #991b1b;
}

/* FAB for Mobile */
.fab {
    position: fixed;
    bottom: 20px;
    right: 20px;
    width: 56px;
    height: 56px;
    border-radius: 50%;
    background: var(--primary);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
    font-size: 24px;
    z-index: 50;
    cursor: pointer;
}

/* Badges */
.badge {
    display: inline-block;
    padding: 4px 10px;
    border-radius: 999px;
    font-size: 0.8rem;
    font-weight: 600;
    line-height: normal;
    text-align: center;
    white-space: nowrap;
    vertical-align: baseline;
}

.badge-success {
    background-color: #d1fae5;
    color: #065f46;
}

.badge-warning {
    background-color: #fef3c7;
    color: #92400e;
}

.badge-info {
    background-color: #dbeafe;
    color: #1e40af;
}

.badge-danger {
    background-color: #fee2e2;
    color: #991b1b;
}