:root {
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
    --color-bg: #1a1a1d;
    --color-text: #f0f0f0;
    --color-border: #444;
    --color-header: #2c2c30;
    --color-time-text: #999;
    --cohort-alpha-border: #1abc9c;
    --cohort-beta-border: #3498db;
    --cohort-gamma-border: #b06dca;
    --tooltip-bg: #333;
    --border-radius: 6px;
}

body {
    font-family: var(--font-sans);
    background-color: var(--color-bg);
    color: var(--color-text);
    margin: 0;
    padding: 20px;
    font-size: 14px;
}

.container {
    max-width: 1200px;
    margin: auto;
}

header {
    text-align: center;
    margin-bottom: 25px;
}

header h1 {
    margin: 0 0 10px 0;
    font-weight: 500;
}

.controls {
    display: flex;
    justify-content: center;
    gap: 15px;
    flex-wrap: wrap;
}

.controls label {
    display: inline-block;
    padding: 10px 20px;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all 0.2s ease-in-out;
    border: 2px solid var(--color-border);
    user-select: none;
    color: var(--color-text);
    font-weight: 500;
}

.controls input[type="checkbox"] {
    display: none;
}

.controls input[type="checkbox"]:checked+label {
    color: #fff;
    font-weight: 600;
    text-shadow: 0 0 5px rgba(0, 0, 0, 0.2);
}

#alpha-toggle:checked+label {
    background-color: var(--cohort-alpha-border);
    border-color: var(--cohort-alpha-border);
}

#beta-toggle:checked+label {
    background-color: var(--cohort-beta-border);
    border-color: var(--cohort-beta-border);
}

#gamma-toggle:checked+label {
    background-color: var(--cohort-gamma-border);
    border-color: var(--cohort-gamma-border);
}

.legend-controls {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 10px 20px;
    margin-top: 20px;
    font-size: 12px;
    align-items: center;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 5px 10px;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: background-color 0.2s, opacity 0.2s;
    opacity: 0.7;
}

.legend-item.active {
    opacity: 1;
    background-color: var(--color-header);
}

.legend-item:hover {
    opacity: 1;
}

.legend-color-box {
    width: 14px;
    height: 14px;
    border-radius: 3px;
}

.clear-filters-btn {
    background: none;
    border: 1px solid var(--color-border);
    color: var(--color-time-text);
    padding: 6px 12px;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: 12px;
    transition: all 0.2s;
}

.clear-filters-btn:hover {
    background-color: var(--color-header);
    color: var(--color-text);
}

.calendar-wrapper {
    position: relative;
}

/* Fixed time labels column that sits on the left of the scrollable calendar */
#time-labels-fixed {
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 32px;
    z-index: 20;
    background-color: var(--color-bg);
    border-right: 1px solid var(--color-border);
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: stretch;
    padding-top: 0;
    /* headers align with calendar headers */
}

.calendar-scroll-container {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: thin;
    scrollbar-color: var(--color-border) var(--color-header);
    border-top: 1px solid var(--color-border);
    border-bottom: 1px solid var(--color-border);
    margin-left: 32px;
    /* leave space for fixed time labels */
}

.calendar-scroll-container::-webkit-scrollbar {
    height: 8px;
}

.calendar-scroll-container::-webkit-scrollbar-track {
    background: var(--color-header);
}

.calendar-scroll-container::-webkit-scrollbar-thumb {
    background-color: var(--color-border);
    border-radius: 4px;
}

.calendar-empty-state {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: var(--color-time-text);
    font-size: 1.2em;
    text-align: center;
    display: none;
    z-index: 15;
}

.calendar {
    display: grid;
    grid-template-rows: auto 1fr;
    gap: 0;
}

.day-header, .time-label-header {
    text-align: center;
    font-weight: 600;
    padding: 10px 0;
    background-color: var(--color-header);
    position: sticky;
    top: 0;
    z-index: 11;
    border-bottom: 1px solid var(--color-border);
}

.time-label-header {
    z-index: 13;
}

.day-header.is-today, .day-column.is-today {
    background-color: rgba(255, 255, 140, 0.07);
}

.day-header.is-weekend, .day-column.is-weekend {
    background-color: rgba(0, 0, 0, 0.15);
}

.time-label-header, .time-labels {
    position: sticky;
    left: 0;
    z-index: 15;
    background-color: var(--color-bg);
    width: 32px;
}

.time-labels {
    display: flex;
    flex-direction: column;
    grid-row: 2;
    grid-column: 1;
    border-right: 1px solid var(--color-border);
    position: sticky;
    left: 0;
    z-index: 15;
    background-color: var(--color-bg);
    width: 32px;
}

.time-labels .hour-label {
    flex-grow: 1;
    position: relative;
    font-size: 12px;
    color: var(--color-time-text);
}

.time-labels .hour-label span {
    position: absolute;
    /* Place the label at the bottom grid line of each hour block (60px tall) */
    top: calc(60px - 0.7em);
    right: 5px;
}

.day-column {
    position: relative;
    background-image: linear-gradient(var(--color-border) 1px, transparent 1px);
    background-size: 100% 60px;
    border-right: 1px solid var(--color-border);
    grid-row: 2;
    min-width: 220px;
}

.holiday-block {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    height: 100%;
    text-align: center;
    padding: 10px;
    box-sizing: border-box;
    background-color: rgba(100, 100, 100, 0.2);
}

.holiday-name {
    font-weight: 600;
    font-size: 1.2em;
}

.class-block {
    position: absolute;
    padding: 5px;
    border-radius: var(--border-radius);
    box-sizing: border-box;
    overflow: hidden;
    font-size: 11px;
    line-height: 1.3;
    border-left: 5px solid;
    transition: all 0.3s ease-in-out;
    margin: 0 2px;
    color: #fff;
    background-repeat: no-repeat;
    background-position: calc(100% - 8px) 50%;
    background-size: 28px 28px;
}

.class-block.faded {
    opacity: 0.15;
}

.class-block:hover {
    filter: brightness(1.2);
    z-index: 5;
    box-shadow: 0 0 15px rgba(0, 0, 0, 0.5);
}

.class-block.cohort-alpha {
    border-color: var(--cohort-alpha-border);
}

.class-block.cohort-beta {
    border-color: var(--cohort-beta-border);
}

.class-block.cohort-gamma {
    border-color: var(--cohort-gamma-border);
}

.class-block.cohort-event {
    border-color: #f59e0b;
    /* A gold/yellow color for events */
    z-index: 10;
    /* Appear above regular cohort classes if overlapping */
}

.class-block-course {
    font-weight: 700;
    font-size: 12px;
}

.class-block-type, .class-block-instructor {
    opacity: 0.9;
}

.class-block-room {
    position: absolute;
    bottom: 4px;
    right: 6px;
    font-weight: 600;
}

.class-block-info {
    background-color: rgba(0, 0, 0, 0.5);
    color: #ffc107;
    font-size: 10px;
    padding: 2px 4px;
    border-radius: 3px;
    margin-top: 4px;
    font-weight: bold;
}

.tooltip {
    position: fixed;
    display: none;
    background-color: var(--tooltip-bg);
    color: var(--color-text);
    padding: 8px 12px;
    border-radius: var(--border-radius);
    font-size: 13px;
    z-index: 100;
    pointer-events: none;
    max-width: 250px;
}

.tooltip-title {
    font-weight: 700;
    margin-bottom: 4px;
}

.tooltip-details span {
    display: block;
}

footer {
    text-align: center;
    margin-top: 20px;
    font-size: 13px;
    color: var(--color-time-text);
}

footer p {
    margin: 5px 0;
}

.scroll-hint {
    display: none;
}

/* --- MOBILE RESPONSIVE STYLES --- */
@media (max-width: 800px) {
    body {
        padding: 10px;
        font-size: 13px;
    }

    header h1 {
        font-size: 1.5em;
    }
}