:root {
    --bg-color: #0d1117;
    --panel-bg: rgba(22, 27, 34, 0.6);
    --border-color: rgba(255, 255, 255, 0.1);
    --text-primary: #c9d1d9;
    --text-secondary: #8b949e;
    --accent-color: #58a6ff;
    --accent-hover: #3182ce;
    --success-color: #238636;
    --success-bg: rgba(35, 134, 54, 0.15);
    --error-color: #f85149;
    --error-bg: rgba(248, 81, 73, 0.1);
    --font-main: 'Inter', sans-serif;
    --font-code: 'Fira Code', monospace;
}

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

body {
    font-family: var(--font-main);
    background: radial-gradient(circle at top right, #1f2937, #0d1117);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
    display: flex;
}

/* Glassmorphism utility */
.glass-panel {
    background: var(--panel-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
}

.app-container {
    display: flex;
    width: 100%;
    height: 100%;
    padding: 24px;
    gap: 24px;
}

/* Sidebar */
.sidebar {
    width: 320px;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.sidebar-header {
    padding: 24px 20px;
    border-bottom: 1px solid var(--border-color);
}

.sidebar-header h2 {
    font-size: 1.8rem;
    font-weight: 700;
    margin-bottom: 4px;
    background: linear-gradient(90deg, #58a6ff, #a371f7);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.sidebar-header p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 16px;
}

.progress-container {
    height: 8px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 8px;
}

.progress-bar {
    height: 100%;
    width: 0%;
    background: linear-gradient(90deg, #2ea043, #3fb950);
    transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.progress-text {
    font-size: 0.85rem !important;
    text-align: right;
    margin-bottom: 0 !important;
    font-weight: 500;
}

.exercise-list {
    list-style: none;
    overflow-y: auto;
    flex: 1;
    padding: 12px;
}

/* Scrollbar styling */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}
::-webkit-scrollbar-track {
    background: transparent;
}
::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.1);
    border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
    background: rgba(255, 255, 255, 0.3);
}

.exercise-item {
    padding: 14px 16px;
    margin-bottom: 8px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s ease;
    border: 1px solid transparent;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.exercise-item:hover {
    background: rgba(255, 255, 255, 0.08);
}

.exercise-item.active {
    background: rgba(88, 166, 255, 0.15);
    border-color: rgba(88, 166, 255, 0.3);
}

.exercise-item .title {
    font-weight: 500;
    font-size: 0.95rem;
}

.exercise-item .status-icon {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8rem;
    font-weight: bold;
}

.status-icon.completed {
    color: var(--success-color);
}
.status-icon.failed {
    color: var(--error-color);
}

/* Main Content */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 20px;
    overflow: hidden;
}

.main-header {
    padding: 24px 32px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.main-header h1 {
    font-size: 1.5rem;
    font-weight: 600;
    letter-spacing: -0.5px;
}

.status-badge {
    padding: 8px 16px;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
    background: rgba(255, 255, 255, 0.1);
}
.status-badge.completed {
    background: var(--success-bg);
    color: #3fb950;
    border: 1px solid var(--success-color);
}
.status-badge.failed {
    background: var(--error-bg);
    color: #ff7b72;
    border: 1px solid var(--error-color);
}

.exercise-body {
    flex: 1;
    display: grid;
    grid-template-columns: 1fr 1fr;
    grid-template-rows: auto 1fr;
    gap: 20px;
    overflow: hidden;
}

.description-panel {
    grid-column: 1 / -1;
    padding: 24px 32px;
    height: auto;
}

.description-panel h3 {
    font-size: 1.05rem;
    color: var(--accent-color);
    margin-bottom: 12px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.description-panel p {
    line-height: 1.6;
    color: var(--text-primary);
    font-size: 1.05rem;
}

.description-panel code {
    background: rgba(255, 255, 255, 0.1);
    padding: 2px 6px;
    border-radius: 4px;
    font-family: var(--font-code);
    font-size: 0.9em;
    color: #a371f7;
}

.editor-panel {
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.editor-header {
    padding: 16px 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    background: rgba(0, 0, 0, 0.2);
}

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

.btn-primary {
    background: linear-gradient(90deg, var(--accent-color), #2f81f7);
    color: #fff;
    border: none;
    padding: 10px 20px;
    border-radius: 8px;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.btn-primary:hover:not(:disabled) {
    box-shadow: 0 4px 12px rgba(88, 166, 255, 0.3);
    transform: translateY(-2px);
}

.btn-primary:disabled {
    background: #444;
    color: #888;
    cursor: not-allowed;
    box-shadow: none;
}

.CodeMirror {
    flex: 1;
    height: auto !important;
    font-family: var(--font-code);
    font-size: 15px;
    background: transparent !important;
}
.CodeMirror-scroll {
    min-height: 200px;
}
.CodeMirror-gutters {
    background: rgba(0, 0, 0, 0.2) !important;
    border-right: 1px solid rgba(255, 255, 255, 0.05) !important;
}

.results-panel {
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.results-panel h3 {
    padding: 16px 24px;
    background: rgba(0, 0, 0, 0.2);
    border-bottom: 1px solid var(--border-color);
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.test-results {
    flex: 1;
    overflow-y: auto;
    padding: 24px;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.empty-state {
    color: var(--text-secondary);
    text-align: center;
    margin-top: 60px;
    font-style: italic;
    font-size: 1.05rem;
}

.test-case {
    background: rgba(0, 0, 0, 0.3);
    border-radius: 8px;
    padding: 16px 20px;
    border-left: 4px solid transparent;
}

.test-case.pass {
    border-left-color: var(--success-color);
}
.test-case.fail {
    border-left-color: var(--error-color);
}

.test-case-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 12px;
    font-family: var(--font-code);
    font-weight: 600;
    font-size: 0.95rem;
}

.test-case-details {
    font-family: var(--font-code);
    font-size: 0.9rem;
    background: rgba(0, 0, 0, 0.2);
    padding: 12px 16px;
    border-radius: 6px;
    border: 1px solid var(--border-color);
}
.detail-row {
    margin-bottom: 6px;
}
.detail-row span {
    color: var(--text-secondary);
    display: inline-block;
    width: 90px;
}

.summary-card {
    margin-top: auto;
    padding: 20px;
    border-radius: 8px;
    text-align: center;
    font-weight: 600;
    font-size: 1.1rem;
    animation: fadeIn 0.5s ease-out;
}
.summary-card.pass {
    background: var(--success-bg);
    color: #3fb950;
    border: 1px solid var(--success-color);
}
.summary-card.fail {
    background: var(--error-bg);
    color: #ff7b72;
    border: 1px solid var(--error-color);
}

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

/* Login Overlay */
.login-overlay {
    position: fixed;
    top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0, 0, 0, 0.85);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 9999;
}
.login-wrapper {
    padding: 40px;
    width: 400px;
    text-align: center;
    display: flex;
    flex-direction: column;
}
.login-wrapper h2 {
    color: var(--text-primary);
    margin-bottom: 8px;
}
.login-wrapper input {
    padding: 14px;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 8px;
    color: #fff;
    font-size: 1rem;
    font-family: inherit;
    outline: none;
    transition: border-color 0.2s;
}
.login-wrapper input:focus {
    border-color: var(--accent-color);
}