:root {
    /* GitHub Dark Theme Contribution Graph Palette */
    --bg-color: #0d1117;
    --text-color: #c9d1d9;
    --text-muted: #8b949e;
    --border-color: #30363d;
    --card-bg: #161b22;
    --primary-color: #238636;
    --primary-hover: #2ea043;
    --danger-color: #da3633;
    --danger-hover: #b62324;
    
    --level-0: #161b22; /* Empty */
    --level-1: #0e4429;
    --level-2: #006d32;
    --level-3: #26a641;
    --level-4: #39d353; /* Most active */

    --square-size: 11px;
    --square-gap: 3px;
    --border-radius: 6px;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.5;
}

.app-container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
}

h1 {
    font-size: 1.5rem;
    font-weight: 600;
}

.subtitle {
    color: var(--text-muted);
    font-size: 0.9rem;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.4rem 0.8rem;
    border-radius: var(--border-radius);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.2s, border-color 0.2s;
    border: 1px solid transparent;
}

.btn.primary {
    background-color: var(--primary-color);
    color: #ffffff;
    border-color: rgba(240, 246, 252, 0.1);
}

.btn.primary:hover {
    background-color: var(--primary-hover);
}

.btn.secondary {
    background-color: var(--card-bg);
    color: var(--text-color);
    border-color: var(--border-color);
}

.btn.secondary:hover {
    background-color: #30363d;
    border-color: #8b949e;
}

.btn.danger {
    background-color: transparent;
    color: var(--danger-color);
    border-color: var(--border-color);
}

.btn.danger:hover {
    background-color: var(--danger-color);
    color: #ffffff;
    border-color: var(--danger-color);
}

.icon-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 0.2rem;
    border-radius: 4px;
}

.icon-btn:hover {
    color: var(--text-color);
    background-color: var(--border-color);
}

.icon-btn i {
    width: 20px;
    height: 20px;
}

.btn i {
    width: 16px;
    height: 16px;
}

/* Controls */
.habit-controls {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
    align-items: center;
    flex-wrap: wrap;
}

.habit-selector {
    padding: 0.4rem 2rem 0.4rem 0.8rem;
    border-radius: var(--border-radius);
    background-color: var(--card-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    font-size: 0.875rem;
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%238b949e' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
    background-repeat: no-repeat;
    background-position: right 0.5rem center;
    background-size: 16px;
    min-width: 200px;
}

.habit-selector:focus {
    outline: none;
    border-color: var(--primary-color);
}

/* Stats */
.stats-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.stat-card {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.stat-label {
    font-size: 0.8rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-color);
}

/* Heatmap Wrapper (Target for Export) */
.heatmap-wrapper {
    background-color: var(--bg-color); /* Matches body */
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    margin-bottom: 2rem;
}

.heatmap-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.heatmap-header h2 {
    font-size: 1rem;
    font-weight: 400;
}

.year-label {
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* Scroll Container for Mobile */
.heatmap-scroll-container {
    overflow-x: auto;
    overflow-y: hidden;
    padding-bottom: 0.5rem; /* Space for scrollbar */
}

.heatmap-scroll-container::-webkit-scrollbar {
    height: 8px;
}
.heatmap-scroll-container::-webkit-scrollbar-track {
    background: var(--bg-color); 
}
.heatmap-scroll-container::-webkit-scrollbar-thumb {
    background: var(--border-color); 
    border-radius: 4px;
}
.heatmap-scroll-container::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted); 
}

.heatmap-grid-container {
    min-width: 750px; /* Force minimum width to show roughly a year */
    display: flex;
    flex-direction: column;
}

.heatmap-months {
    display: flex;
    font-size: 0.75rem;
    color: var(--text-muted);
    height: 1.5rem;
    margin-left: 28px; /* Offset for weekdays */
}

.month-label {
    position: absolute; /* Using relative container strategy in JS */
}

.heatmap-body {
    display: flex;
}

.heatmap-weekdays {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    font-size: 0.75rem;
    color: var(--text-muted);
    padding-right: 8px;
    height: calc((var(--square-size) * 7) + (var(--square-gap) * 6));
    padding-top: calc(var(--square-size) * 1 + var(--square-gap)); /* Align Mon */
    padding-bottom: calc(var(--square-size) * 1 + var(--square-gap)); /* Align Fri */
    box-sizing: border-box;
}

.heatmap-weekdays span {
    line-height: var(--square-size);
}

.heatmap {
    display: grid;
    grid-template-columns: repeat(53, 1fr);
    gap: var(--square-gap);
    height: max-content;
}

.week {
    display: grid;
    grid-template-rows: repeat(7, var(--square-size));
    gap: var(--square-gap);
}

.square {
    width: var(--square-size);
    height: var(--square-size);
    border-radius: 2px;
    cursor: pointer;
    transition: transform 0.1s, opacity 0.2s;
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.square:hover {
    transform: scale(1.2);
    box-shadow: 0 0 0 1px var(--text-color);
    z-index: 10;
    position: relative;
}

/* Colors */
.square.level-0 { background-color: var(--level-0); }
.square.level-1 { background-color: var(--level-1); }
.square.level-2 { background-color: var(--level-2); }
.square.level-3 { background-color: var(--level-3); }
.square.level-4 { background-color: var(--level-4); }

.heatmap-footer {
    display: flex;
    justify-content: flex-end;
    align-items: center;
    gap: 0.5rem;
    margin-top: 1rem;
    font-size: 0.75rem;
    color: var(--text-muted);
}

.legend {
    display: flex;
    gap: var(--square-gap);
}

.legend .square {
    cursor: default;
}
.legend .square:hover {
    transform: none;
    box-shadow: none;
}

/* Tooltip */
.tooltip {
    position: absolute;
    background-color: var(--text-color);
    color: var(--bg-color);
    padding: 0.5rem 0.75rem;
    border-radius: var(--border-radius);
    font-size: 0.75rem;
    font-weight: 500;
    pointer-events: none;
    z-index: 100;
    opacity: 0;
    transition: opacity 0.1s;
    white-space: nowrap;
    transform: translate(-50%, -100%);
    margin-top: -8px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.3);
}

.tooltip::after {
    content: '';
    position: absolute;
    top: 100%;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: var(--text-color) transparent transparent transparent;
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(2px);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    opacity: 1;
    transition: opacity 0.2s;
}

.modal.hidden {
    opacity: 0;
    pointer-events: none;
}

.modal-content {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    width: 100%;
    max-width: 400px;
    padding: 1.5rem;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
    transform: translateY(0);
    transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.modal.hidden .modal-content {
    transform: translateY(-20px);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.modal-header h2 {
    font-size: 1.25rem;
    font-weight: 500;
}

.modal-body {
    margin-bottom: 1.5rem;
}

.modal-body label {
    display: block;
    margin-bottom: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-muted);
}

.modal-body input {
    width: 100%;
    padding: 0.5rem 0.75rem;
    border-radius: var(--border-radius);
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    color: var(--text-color);
    font-size: 1rem;
}

.modal-body input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: 0.5rem;
}

@media (max-width: 600px) {
    .habit-controls {
        flex-direction: column;
        align-items: stretch;
    }
    
    header {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }
}