:root {
    --bg-color: #f0f2f5;
    --card-bg-color: #ffffff;
    --text-color: #1c1e21;
    --primary-color: #1877f2;
    --primary-hover: #166fe5;
    --border-color: #dddfe2;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --color-green: #42b72a;
    --color-yellow: #f5c33b;
    --color-red: #fa3e3e;
    --color-grey: #606770;
}

body {
    font-family: 'Poppins', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    line-height: 1.6;
}

#app-container {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header {
    background-color: var(--card-bg-color);
    padding: 0.75rem 2rem;
    box-shadow: 0 2px 4px var(--shadow-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 1000;
}

header h1 {
    margin: 0;
    font-size: 1.5rem;
    color: var(--primary-color);
}

nav button {
    background-color: transparent;
    border: none;
    color: var(--color-grey);
    padding: 0.75rem 1rem;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 600;
    font-size: 1rem;
    margin-left: 0.5rem;
    transition: background-color 0.2s ease, color 0.2s ease;
}

nav button.active, nav button:hover {
    background-color: #e7f3ff;
    color: var(--primary-color);
}

main {
    padding: 1.5rem;
    max-width: 1400px;
    width: 100%;
    margin: 0 auto;
    box-sizing: border-box;
    flex-grow: 1;
}

.view { display: none; }
.view.active { display: block; animation: fadeIn 0.3s ease-in-out; }

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.dashboard-grid {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 1.5rem;
}

.card {
    background-color: var(--card-bg-color);
    border-radius: 8px;
    box-shadow: 0 1px 2px var(--shadow-color);
    overflow: hidden;
}

.card-content {
    padding: 1.25rem;
}

.card-content h2 {
    margin-top: 0;
    margin-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.75rem;
    font-size: 1.2rem;
}

.stat-grid { display: grid; grid-template-columns: 1fr 1fr; text-align: center; }
.stat-label { font-size: 0.9rem; color: var(--color-grey); }
.stat-value { font-size: 2.25rem; font-weight: 700; color: var(--primary-color); margin: 0; }

.semester-stat { display: flex; justify-content: space-between; padding: 0.4rem 0; font-size: 0.9rem; }
#at-risk-placeholder { color: var(--color-grey); text-align: center; padding: 1rem; font-style: italic; }
.at-risk-subject { padding: 0.75rem; border-left: 4px solid var(--color-red); background-color: #fff0f0; border-radius: 6px; margin-bottom: 0.5rem; display: flex; justify-content: space-between; align-items: center; }

.table-container { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; }
th, td { padding: 0.75rem 1rem; text-align: left; border-bottom: 1px solid var(--border-color); vertical-align: middle; }
th { font-weight: 600; font-size: 0.9rem; color: var(--color-grey); text-transform: uppercase; }
.subject-list-row td { font-weight: 500; }
td:nth-child(3), td:nth-child(4) { text-align: center; font-weight: 600; }

.log-toggle-btn { background: none; border: none; font-size: 1.25rem; cursor: pointer; color: var(--primary-color); padding: 0; width: 32px; height: 32px; border-radius: 50%; display: inline-flex; justify-content: center; align-items: center; transition: background-color 0.2s, transform 0.2s; }
.log-toggle-btn:hover { background-color: #f0f2f5; }

#library-list .book-item { padding: 0.75rem 0; border-bottom: 1px solid var(--border-color); }
.book-info p { margin: 0; }
.book-title { font-weight: 600; }
.book-due-date.overdue { color: var(--color-red); font-weight: 600; }
.book-actions { margin-top: 0.5rem; display: flex; gap: 0.5rem; }
.book-actions button { flex-grow: 1; padding: 0.4rem; font-size: 0.8rem; border-radius: 4px; border: 1px solid; cursor: pointer; }
.book-actions .return-book-btn { background-color: var(--color-green); color: white; border-color: var(--color-green); }
.book-actions .renew-book-btn { background-color: transparent; color: var(--primary-color); border-color: var(--primary-color); }

.full-width { display: block; width: 100%; text-align: center; background-color: var(--primary-color); color: white; border: none; padding: 0.75rem; border-radius: 6px; cursor: pointer; font-size: 0.9rem; margin-top: 1rem; font-weight: 600; }
#data-management-card .full-width { background-color: var(--color-grey); }

.daily-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 1rem; }
.daily-header h2 { margin: 0; text-align: center; flex-grow: 1; font-size: 1.5rem; }
.daily-header button { background: var(--card-bg-color); border: 1px solid var(--border-color); border-radius: 50%; width: 40px; height: 40px; cursor: pointer; font-size: 1.2rem; transition: background-color 0.2s; }
.daily-header button:hover { background-color: #f0f2f5; }

.day-status-bar { text-align: center; margin-bottom: 1rem; }
.day-status-bar button { width: 100%; padding: 0.75rem; background-color: #e7f3ff; border: 1px solid var(--primary-color); color: var(--primary-color); border-radius: 6px; font-size: 1rem; cursor: pointer; font-weight: 600; transition: background-color 0.2s; }
.day-status-bar button:hover { background-color: #dbeaff; }

.day-actions { margin: 1.5rem 0; display: flex; gap: 0.5rem; justify-content: center; align-items: center; }
.date-picker-wrapper { position: relative; }
.calendar-icon { position: absolute; right: 10px; top: 50%; transform: translateY(-50%); font-size: 1.2rem; pointer-events: none; opacity: 0.5; }
#date-picker { padding: 0.5rem 1rem; border: 1px solid var(--border-color); border-radius: 6px; font-family: 'Poppins', sans-serif; font-size: 1rem; }
.day-actions button { background-color: var(--color-grey); color: white; border: none; padding: 0.6rem 1rem; border-radius: 6px; cursor: pointer; font-weight: 600; }

.class-item { background: var(--card-bg-color); padding: 1rem 1.5rem; border-radius: 8px; margin-bottom: 1rem; box-shadow: 0 1px 2px var(--shadow-color); display: flex; justify-content: space-between; align-items: center; }
.class-info { flex-grow: 1; }
.class-info p { margin: 0; }
.class-info .class-time { font-size: 0.9em; color: var(--color-grey); }
.class-actions .btn { border: none; color: white; padding: 0.5rem 1rem; border-radius: 16px; font-weight: 600; cursor: pointer; margin-left: 0.5rem; transition: filter 0.2s; }
.class-actions .btn:not(.active) { filter: grayscale(80%) opacity(70%); }
.class-actions .btn.active { box-shadow: 0 2px 4px rgba(0,0,0,0.2); }
.btn-attended { background-color: var(--color-green); }
.btn-missed { background-color: var(--color-red); }
.btn-cancelled { background-color: var(--color-grey); }

.modal-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background-color: rgba(0,0,0,0.6); z-index: 2000; display: none; justify-content: center; align-items: center; opacity: 0; transition: opacity 0.2s; }
.modal-overlay.visible { display: flex; opacity: 1; }
.modal-content { background-color: white; padding: 2rem; border-radius: 8px; box-shadow: 0 5px 15px rgba(0,0,0,0.3); width: 90%; max-width: 500px; transform: scale(0.95); transition: transform 0.2s; }
.modal-overlay.visible .modal-content { transform: scale(1); }
.modal-content input[type="text"] { width: 100%; padding: 0.75rem; margin-bottom: 1rem; border: 1px solid var(--border-color); border-radius: 6px; box-sizing: border-box; font-size: 1rem; }
.modal-actions { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 1.5rem; }
.modal-btn { padding: 0.75rem; border: none; border-radius: 6px; cursor: pointer; font-weight: 600; background-color: var(--primary-color); color: white; }
.modal-btn.secondary { background-color: var(--color-grey); }

.autocomplete-wrapper { position: relative; }
.autocomplete-items { position: absolute; border: 1px solid #ddd; border-top: none; z-index: 99; top: 100%; left: 0; right: 0; background-color: white; max-height: 150px; overflow-y: auto; }
.autocomplete-items div { padding: 10px; cursor: pointer; border-bottom: 1px solid #ddd; }
.autocomplete-items div:hover { background-color: #e9e9e9; }
.autocomplete-active { background-color: DodgerBlue !important; color: #ffffff; }

.slide-panel { position: fixed; top: 0; right: 0; width: 100%; max-width: 600px; height: 100%; background-color: var(--bg-color); z-index: 1500; transform: translateX(100%); transition: transform 0.3s ease-in-out; box-shadow: -2px 0 8px rgba(0,0,0,0.15); display: flex; flex-direction: column; }
.slide-panel.visible { transform: translateX(0); }
.panel-header { display: flex; align-items: center; padding: 0.75rem 1rem; background-color: var(--card-bg-color); border-bottom: 1px solid var(--border-color); flex-shrink: 0; }
.panel-header button { background: none; border: none; font-size: 1.5rem; cursor: pointer; padding-right: 1rem; }
.panel-content { padding: 1.5rem; overflow-y: auto; flex-grow: 1; }
.log-filters { margin-bottom: 1rem; }
.log-filters button { margin-right: 0.5rem; padding: 0.3rem 0.8rem; border: 1px solid var(--border-color); background: white; border-radius: 16px; cursor: pointer; }
.log-filters button.active { background: var(--primary-color); color: white; border-color: var(--primary-color); }
.log-table { background: var(--card-bg-color); border-radius: 8px; overflow: hidden; }

footer { text-align: center; padding: 1rem; margin-top: auto; color: #888; font-size: 0.8rem; flex-shrink: 0; }

@media (max-width: 900px) {
    .dashboard-grid { grid-template-columns: 1fr; }
    header { padding: 0.75rem 1rem; }
    main { padding: 1rem; }
}