* {
	box-sizing: border-box;
}

body {
	margin: 0;
	font-family: Arial, sans-serif;
	background: #f3f4f6;
	color: #111827;
}

button,
select,
textarea {
	font: inherit;
}

.app-shell {
	min-height: 100vh;
	padding: 20px;
}

.topbar {
	display: flex;
	justify-content: space-between;
	align-items: end;
	gap: 16px;
	margin-bottom: 20px;
}

.topbar h1 {
	margin: 0 0 6px;
	font-size: 28px;
}

.topbar p {
	margin: 0;
	color: #4b5563;
}

.problem-picker {
	display: flex;
	flex-direction: column;
	gap: 6px;
	min-width: 260px;
}

.problem-picker select {
	padding: 10px 12px;
	border: 1px solid #d1d5db;
	border-radius: 10px;
	background: #fff;
}

.workspace {
	display: grid;
	grid-template-columns: minmax(320px, 1fr) minmax(360px, 1fr);
	gap: 20px;
}

.panel {
	background: #fff;
	border: 1px solid #e5e7eb;
	border-radius: 16px;
	padding: 20px;
	box-shadow: 0 8px 24px rgba(17, 24, 39, 0.06);
}

.problem-panel,
.editor-panel {
	min-height: calc(100vh - 120px);
}

.problem-header,
.editor-header,
.results-header {
	display: flex;
	justify-content: space-between;
	align-items: center;
	gap: 12px;
}

.problem-header h2,
.editor-header h2,
.results-header h3 {
	margin: 0;
}

.problem-description {
	line-height: 1.6;
	color: #1f2937;
}

.difficulty-badge {
	padding: 6px 10px;
	border-radius: 999px;
	font-size: 14px;
	font-weight: 700;
}

.difficulty-easy {
	background: #dcfce7;
	color: #166534;
}

.difficulty-medium {
	background: #fef3c7;
	color: #92400e;
}

.difficulty-hard {
	background: #fee2e2;
	color: #991b1b;
}

.problem-section {
	margin-top: 24px;
}

.problem-section h3 {
	margin-bottom: 12px;
}

.example-list {
	display: grid;
	gap: 12px;
}

.example-card {
	background: #f9fafb;
	border: 1px solid #e5e7eb;
	border-radius: 12px;
	padding: 12px;
}

.example-card p {
	margin: 0;
	line-height: 1.5;
}

.constraints-list {
	margin: 0;
	padding-left: 18px;
	color: #374151;
}

.muted-text {
	color: #6b7280;
}

.editor-panel {
	display: flex;
	flex-direction: column;
	gap: 16px;
}

#run-button {
	border: 0;
	border-radius: 10px;
	padding: 10px 14px;
	background: #2563eb;
	color: #fff;
	cursor: pointer;
	font-weight: 700;
}

#run-button:disabled {
	opacity: 0.6;
	cursor: wait;
}

#code-editor {
	width: 100%;
	flex: 1;
	min-height: 420px;
	resize: vertical;
	border: 1px solid #d1d5db;
	border-radius: 14px;
	padding: 16px;
	background: #111827;
	color: #f9fafb;
	line-height: 1.5;
	font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
	font-size: 14px;
}

.results-section {
	border-top: 1px solid #e5e7eb;
	padding-top: 16px;
}

.results-output {
	display: grid;
	gap: 10px;
	margin-top: 12px;
}

.result-card {
	border: 1px solid #e5e7eb;
	border-radius: 12px;
	padding: 12px;
	background: #f9fafb;
}

.result-card.pass {
	border-color: #86efac;
	background: #f0fdf4;
}

.result-card.fail {
	border-color: #fca5a5;
	background: #fef2f2;
}

.result-card p {
	margin: 0 0 6px;
	line-height: 1.45;
}

.result-card p:last-child {
	margin-bottom: 0;
}

.result-label {
	font-weight: 700;
}

@media (max-width: 960px) {
	.topbar,
	.workspace,
	.problem-header,
	.editor-header,
	.results-header {
		grid-template-columns: 1fr;
		flex-direction: column;
		align-items: stretch;
	}

	.problem-panel,
	.editor-panel {
		min-height: auto;
	}

	#code-editor {
		min-height: 320px;
	}
}