:root {
    --bg-dark: #09090b;
    --bg-card: #18181b;
    --border-color: #27272a;
    --text-main: #f4f4f5;
    --text-muted: #a1a1aa;
    
    /* Premium Emerald Green */
    --heatmap-empty: #27272a;
    --heatmap-active: #10b981;
    --heatmap-active-glow: rgba(16, 185, 129, 0.4);
    --heatmap-active-hover: #059669;
    
    --transition-speed: 0.2s;
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-main);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 2rem;
}

.app-container {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    padding: 3rem;
    max-width: 1000px;
    width: 100%;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
}

header {
    margin-bottom: 3rem;
    text-align: center;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 0.5rem;
    background: linear-gradient(135deg, #fff 0%, #a1a1aa 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.subtitle {
    color: var(--text-muted);
    font-size: 1.1rem;
    margin-bottom: 2rem;
}

.stats-container {
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-top: 1.5rem;
}

.stat-box {
    display: flex;
    flex-direction: column;
    align-items: center;
    background: rgba(255, 255, 255, 0.03);
    padding: 1rem 2rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
}

.stat-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--heatmap-active);
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-top: 0.25rem;
}

.heatmap-wrapper {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.months-header {
    display: grid;
    grid-template-columns: repeat(12, 1fr);
    width: 100%;
    margin-bottom: 0.5rem;
    padding-left: 20px; /* Aligns with grid nicely usually */
    font-size: 0.8rem;
    color: var(--text-muted);
}

.month-label {
    text-align: left;
}

.heatmap-grid {
    display: grid;
    /* 53 columns for 53 weeks in a year */
    grid-template-columns: repeat(53, 1fr);
    grid-template-rows: repeat(7, 1fr);
    gap: 5px;
    grid-auto-flow: column; /* Fill top-to-bottom, then next column */
}

.day-block {
    width: 14px;
    height: 14px;
    background-color: var(--heatmap-empty);
    border-radius: 3px;
    cursor: pointer;
    transition: all var(--transition-speed) ease;
    position: relative;
}

.day-block:hover {
    transform: scale(1.2);
    box-shadow: 0 0 10px rgba(255, 255, 255, 0.1);
    z-index: 10;
    border-color: rgba(255, 255, 255, 0.3);
}

.day-block.active {
    background-color: var(--heatmap-active);
    box-shadow: 0 0 8px var(--heatmap-active-glow);
}

.day-block.active:hover {
    background-color: var(--heatmap-active-hover);
    box-shadow: 0 0 12px var(--heatmap-active-glow);
}

.day-block.future {
    opacity: 0.3;
    cursor: not-allowed;
}

.day-block.future:hover {
    transform: none;
    box-shadow: none;
}

.heatmap-legend {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-top: 2rem;
    font-size: 0.85rem;
    color: var(--text-muted);
    align-self: flex-end;
}

.legend-box {
    width: 14px;
    height: 14px;
    border-radius: 3px;
    display: inline-block;
}

.legend-box.empty { background-color: var(--heatmap-empty); }
.legend-box.active { background-color: var(--heatmap-active); box-shadow: 0 0 8px var(--heatmap-active-glow); }

/* Tooltip */
.tooltip {
    position: absolute;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    padding: 0.5rem 0.75rem;
    border-radius: 6px;
    font-size: 0.85rem;
    color: var(--text-main);
    pointer-events: none;
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
    z-index: 100;
    transition: opacity 0.15s ease;
    text-align: center;
    white-space: nowrap;
}

.tooltip.hidden {
    opacity: 0;
}

.tooltip span.date {
    display: block;
    color: var(--text-muted);
    font-size: 0.75rem;
    margin-bottom: 0.2rem;
}