:root {
  --bg-color: #0d1117;
  --panel-bg: rgba(22, 27, 34, 0.7);
  --border-color: #30363d;
  --text-primary: #e6edf3;
  --text-secondary: #8b949e;
  --primary-accent: #2f81f7;
  --primary-hover: #1f6feb;
  --danger-accent: #f85149;
  --success-accent: #2ea043;
  --canvas-bg: #010409;
}

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

body {
  font-family: 'Inter', sans-serif;
  background-color: var(--bg-color);
  color: var(--text-primary);
  height: 100vh;
  overflow: hidden;
}

.app-container {
  display: flex;
  height: 100vh;
  width: 100vw;
}

/* Sidebar Styling */
.sidebar {
  width: 380px;
  background-color: var(--panel-bg);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  padding: 24px;
  gap: 24px;
  box-shadow: 4px 0 16px rgba(0,0,0,0.5);
  backdrop-filter: blur(10px);
  z-index: 10;
  overflow-y: auto;
}

header h1 {
  font-size: 24px;
  font-weight: 600;
  letter-spacing: -0.5px;
}

header .subtitle {
  font-size: 13px;
  color: var(--text-secondary);
  margin-top: 4px;
}

.panel {
  display: flex;
  flex-direction: column;
  gap: 16px;
  background: rgba(255,255,255,0.02);
  padding: 16px;
  border-radius: 12px;
  border: 1px solid rgba(255,255,255,0.05);
}

.flex-fill {
  flex-grow: 1;
}

.panel h3 {
  font-size: 14px;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-secondary);
}

/* Form Elements */
.input-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.input-group label {
  font-size: 13px;
  color: var(--text-secondary);
}

input[type="number"] {
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  padding: 10px 14px;
  border-radius: 6px;
  font-family: inherit;
  font-size: 14px;
  outline: none;
  transition: border-color 0.2s;
}

input[type="number"]:focus {
  border-color: var(--primary-accent);
}

.upload-btn {
  background-color: var(--border-color);
  color: var(--text-primary);
  padding: 10px 14px;
  border-radius: 6px;
  text-align: center;
  font-size: 14px;
  cursor: pointer;
  transition: background-color 0.2s;
  display: block;
}

.upload-btn:hover {
  background-color: #404750;
}

.status-msg {
  font-size: 12px;
  color: var(--success-accent);
}

/* Tool Buttons */
.tool-group {
  display: flex;
  gap: 8px;
}

.tool-btn {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 10px;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s;
  font-size: 13px;
  font-family: inherit;
}

.tool-btn:hover {
  background: rgba(255,255,255,0.05);
  color: var(--text-primary);
}

.tool-btn.active {
  background: rgba(47, 129, 247, 0.15);
  border-color: var(--primary-accent);
  color: var(--primary-accent);
}

.tool-hint {
  font-size: 12px;
  color: var(--text-secondary);
  font-style: italic;
}

/* Action Buttons */
.action-group {
  display: flex;
  gap: 8px;
  margin-top: 8px;
}

.action-btn {
  flex: 1;
  padding: 10px;
  border-radius: 6px;
  border: none;
  font-family: inherit;
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  transition: filter 0.2s;
}

.action-btn:hover {
  filter: brightness(1.2);
}

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

.clear-btn {
  background-color: transparent;
  border: 1px solid var(--danger-accent);
  color: var(--danger-accent);
}

/* Results Pane */
.results-pane {
  display: flex;
  flex-direction: column;
  gap: 8px;
  overflow-y: auto;
  max-height: 300px;
}

.empty-state {
  font-size: 13px;
  color: var(--text-secondary);
  text-align: center;
  padding: 20px 0;
}

.result-card {
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  padding: 12px;
  border-radius: 6px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.result-card .color-indicator {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  display: inline-block;
  margin-right: 8px;
  align-self: center;
}

.result-card .area {
  font-weight: 600;
  color: var(--primary-accent);
}

/* Canvas Area */
.canvas-container {
  flex-grow: 1;
  position: relative;
  background-color: var(--canvas-bg);
  cursor: crosshair;
  overflow: hidden;
  /* Grid pattern background */
  background-image: 
    linear-gradient(rgba(255,255,255,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.03) 1px, transparent 1px);
  background-size: 40px 40px;
}

canvas {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

.tooltip {
  position: absolute;
  background: rgba(0,0,0,0.8);
  color: white;
  padding: 4px 8px;
  border-radius: 4px;
  font-size: 12px;
  pointer-events: none;
  display: none;
  z-index: 100;
  transform: translate(-50%, -100%);
  margin-top: -10px;
  backdrop-filter: blur(4px);
  border: 1px solid rgba(255,255,255,0.1);
}