@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

:root {
    --primary: #4f46e5;      /* Indigo 600 */
    --primary-hover: #4338ca;/* Indigo 700 */
    --secondary: #10b981;    /* Emerald 500 */
    --secondary-hover: #059669; /* Emerald 600 */
    --danger: #ef4444;       /* Red 500 */
    --danger-hover: #dc2626; /* Red 600 */
    --warning: #f59e0b;      /* Amber 500 */
    --warning-hover: #d97706;/* Amber 600 */
    --info: #0ea5e9;         /* Sky 500 */
    --bg-color: #f8fafc;     /* Slate 50 */
    --surface: #ffffff;      /* White */
    --text-main: #1e293b;    /* Slate 800 */
    --text-muted: #64748b;   /* Slate 500 */
    --border: #e2e8f0;       /* Slate 200 */
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-glass: 0 8px 32px 0 rgba(31, 38, 135, 0.07);
    --shadow-glass: 0 8px 32px 0 rgba(31, 38, 135, 0.07);
    --radius: 12px;
    --nav-bg: rgba(255, 255, 255, 0.85);
    --nav-border: rgba(255, 255, 255, 0.3);
    --bg-muted: #f1f5f9;     
    --bg-hover: #e2e8f0;     
    --border-hover: #cbd5e1; 
    --bg-selected: #eff6ff;
}

[data-theme="dark"] {
    --bg-color: #0f172a;     /* Slate 900 */
    --surface: #1e293b;      /* Slate 800 */
    --text-main: #f8fafc;    /* Slate 50 */
    --text-muted: #94a3b8;   /* Slate 400 */
    --border: #334155;       /* Slate 700 */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.5);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -2px rgba(0, 0, 0, 0.2);
    --shadow-glass: 0 8px 32px 0 rgba(0, 0, 0, 0.4);
    --nav-bg: rgba(30, 41, 59, 0.85);
    --nav-border: rgba(255, 255, 255, 0.1);
    --primary: #818cf8;      /* Brighter Indigo */
    --primary-hover: #6366f1;
    --bg-muted: #0f172a;     /* Darker background for muted areas */
    --bg-hover: #334155;     /* Slate 700 */
    --border-hover: #475569; /* Slate 600 */
    --bg-selected: rgba(99, 102, 241, 0.15); /* Translucent indigo */
}

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    margin: 0;
    padding: 0;
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
}

/* Glassmorphism Navbar */
nav {
    background-color: var(--nav-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--nav-border);
    box-shadow: var(--shadow-sm);
    padding: 16px 40px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    z-index: 100;
}
nav .logo {
    font-size: 24px;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary), var(--info));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    cursor: pointer;
}
nav .nav-links a {
    color: var(--text-muted);
    font-weight: 600;
    margin-left: 24px;
    text-decoration: none;
    transition: color 0.2s ease;
    font-size: 15px;
}
nav .nav-links a:hover {
    color: var(--primary);
}

.container {
    padding: 40px 20px;
    max-width: 1200px;
    margin: 0 auto;
}

/* Dashboard Layout */
.dashboard {
    display: flex;
    gap: 30px;
}

/* Elevated Cards */
.sidebar, .workspace, .about-container, .form-container {
    background-color: var(--surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border);
    padding: 30px;
}

.sidebar {
    width: 28%;
    flex-shrink: 0;
}
.workspace {
    width: 72%;
    flex-grow: 1;
}

/* General Headings */
h2, h3 {
    color: var(--text-main);
    margin-top: 0;
    font-weight: 700;
}

/* Flash Messages */
.flashes {
    list-style: none;
    padding: 0;
    margin-bottom: 20px;
}
.flash {
    padding: 12px 20px;
    border-radius: 8px;
    margin-bottom: 10px;
    font-weight: 500;
    box-shadow: var(--shadow-sm);
}
.flash.success {
    background-color: #d1fae5;
    color: #065f46;
    border: 1px solid #10b981;
}
.flash.danger {
    background-color: #fee2e2;
    color: #991b1b;
    border: 1px solid #ef4444;
}

/* Reusable Button Classes */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 8px 16px;
    border-radius: 8px;
    font-weight: 600;
    font-size: 14px;
    cursor: pointer;
    border: none;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: var(--shadow-sm);
    text-decoration: none;
}
.btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}
.btn:active {
    transform: translateY(0);
}
.btn-primary { background: linear-gradient(135deg, var(--primary), #6366f1); color: white; }
.btn-primary:hover { box-shadow: 0 6px 15px rgba(79, 70, 229, 0.3); }
.btn-success { background-color: var(--secondary); color: white; }
.btn-success:hover { background-color: var(--secondary-hover); }
.btn-danger { background-color: var(--danger); color: white; }
.btn-danger:hover { background-color: var(--danger-hover); }
.btn-warning { background-color: var(--warning); color: white; }
.btn-warning:hover { background-color: var(--warning-hover); }
.btn-info { background-color: var(--info); color: white; }
.btn-info:hover { background-color: #0284c7; }
.btn-outline { background-color: transparent; border: 1px solid var(--border); color: var(--text-main); box-shadow: none; }
.btn-outline:hover { background-color: var(--bg-hover); border-color: var(--border-hover); }
.btn-icon { padding: 8px; border-radius: 6px; font-size: 14px; }

button {
    font-family: 'Inter', sans-serif;
}

/* File & Project Lists */
ul {
    list-style: none;
    padding: 0;
    margin: 0;
}
.project-list li {
    margin-bottom: 12px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}
.project-link {
    flex: 1;
    padding: 12px 16px;
    border-radius: 8px;
    text-decoration: none;
    background-color: var(--bg-muted);
    color: var(--text-main);
    font-weight: 500;
    transition: all 0.2s ease;
    border: 1px solid transparent;
}
.project-link:hover {
    background-color: var(--bg-hover);
}
.project-link.active {
    background: linear-gradient(135deg, var(--primary), #6366f1);
    color: white;
    font-weight: 600;
    box-shadow: 0 4px 10px rgba(79, 70, 229, 0.3);
}

.file-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px;
    border-bottom: 1px solid var(--border);
    transition: background-color 0.2s ease;
}
.file-item:last-child {
    border-bottom: none;
}
.file-item:hover {
    background-color: var(--bg-muted);
    border-radius: 8px;
}
.file-name {
    text-decoration: none;
    color: var(--primary);
    font-weight: 500;
    flex-grow: 1;
    margin-left: 12px;
}
.file-name:hover {
    text-decoration: underline;
}

/* Forms & Inputs */
input[type="text"], input[type="number"], input[type="password"] {
    width: 100%;
    padding: 12px 14px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 15px;
    box-sizing: border-box;
    transition: all 0.2s ease;
    background-color: var(--bg-color);
    color: var(--text-main);
}
input[type="text"]:focus, input[type="number"]:focus, input[type="password"]:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.15);
    outline: none;
    background-color: var(--surface);
}

.upload-form {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 20px;
    flex-wrap: wrap;
    background: var(--bg-muted);
    padding: 15px;
    border-radius: 8px;
    border: 1px dashed var(--border-hover);
}

/* Questions / Test Area */
.question-block {
    display: block;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 24px;
    margin-bottom: 20px;
    background-color: var(--surface);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    box-shadow: var(--shadow-sm);
    position: relative;
}
.question-block:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
    border-color: #cbd5e1;
}
.question-block h3 {
    font-size: 18px;
    color: var(--text-main);
    margin-bottom: 18px;
    line-height: 1.4;
}

/* Option Labels */
.question-block label {
    display: flex !important;
    align-items: center;
    padding: 12px 16px;
    margin-bottom: 10px;
    background-color: var(--bg-color);
    border-radius: 8px;
    border: 1px solid transparent;
    cursor: pointer;
    transition: all 0.2s ease-in-out;
    color: var(--text-main);
}
.question-block label:hover {
    box-shadow: var(--shadow-sm);
    background-color: var(--surface);
    border-color: var(--border);
}
.question-block input[type="radio"],
.question-block input[type="checkbox"] {
    margin-left: 0;
    margin-right: 14px;
    transform: scale(1.2);
    accent-color: var(--primary);
    cursor: pointer;
}
.question-block label:has(input:checked) {
    background-color: var(--bg-selected);
    border-color: var(--primary);
    font-weight: 600;
    box-shadow: 0 2px 8px rgba(79, 70, 229, 0.1);
    color: var(--primary);
}

/* Feedback blocks */
.feedback {
    margin-top: 15px;
    padding: 15px;
    border-radius: 8px;
    display: none;
    font-size: 14px;
    line-height: 1.6;
}
.feedback p { margin: 5px 0; }
.feedback.correct {
    background-color: #f0fdf4;
    color: #166534;
    border: 1px solid #bbf7d0;
}
.feedback.incorrect {
    background-color: #fef2f2;
    color: #991b1b;
    border: 1px solid #fecaca;
}

/* Centered Forms (Login/Register/About) */
.form-container, .about-container {
    max-width: 450px;
    margin: 60px auto;
    text-align: center;
}
.about-container { max-width: 650px; text-align: left; }
.form-group {
    margin-bottom: 20px;
    text-align: left;
}
.form-group label {
    display: block;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-main);
    font-size: 14px;
}
.form-container h2 { margin-bottom: 25px; }
.form-container button { width: 100%; padding: 12px; font-size: 16px; }

/* Modal */
#preview-modal {
    backdrop-filter: blur(5px);
}
#modal-body {
    scrollbar-width: thin;
    scrollbar-color: var(--border) transparent;
}
#modal-body::-webkit-scrollbar {
    width: 6px;
}
#modal-body::-webkit-scrollbar-thumb {
    background-color: var(--border);
    border-radius: 10px;
}

/* Loading Animation */
.modern-loader {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 60px 40px;
    background: var(--bg-muted);
    border-radius: var(--radius);
    box-shadow: inset var(--shadow-sm);
    border: 1px dashed var(--border-hover);
    text-align: center;
}

.spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--border);
    border-bottom-color: var(--primary);
    border-radius: 50%;
    display: inline-block;
    box-sizing: border-box;
    animation: rotation 1s linear infinite;
    margin-bottom: 24px;
}

@keyframes rotation {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.modern-loader p {
    color: var(--primary);
    font-weight: 600;
    font-size: 16px;
    margin: 0;
    animation: pulse 1.8s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 0.6; transform: scale(0.98); }
    50% { opacity: 1; transform: scale(1); }
}