/* Variables Definition */
:root {
    /* Light Mode (Default) - Minimal Black & White */
    --bg-color: #fafafa;
    --surface-color: #ffffff;
    --text-primary: #111111;
    --text-secondary: #666666;
    --border-color: #e5e5e5;
    --accent-color: #000000;
    --accent-hover: #333333;
    --accent-text: #ffffff;
    --danger-color: #ff3333;
    --danger-hover: #cc0000;
    --success-bg: #e6ffed;
    --success-text: #006622;
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 16px;
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.08);
    --transition: 0.2s ease-in-out;
}

body.dark-mode {
    --bg-color: #000000;
    --surface-color: #111111;
    --text-primary: #ffffff;
    --text-secondary: #999999;
    --border-color: #222222;
    --accent-color: #ffffff;
    --accent-hover: #cccccc;
    --accent-text: #000000;
    --danger-color: #ff5555;
    --danger-hover: #ff3333;
    --success-bg: #003311;
    --success-text: #44ff88;
    --shadow-sm: 0 2px 8px rgba(255, 255, 255, 0.02);
    --shadow-md: 0 4px 16px rgba(255, 255, 255, 0.04);
}

/* Global Reset & Base */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.5;
    transition: background-color var(--transition), color var(--transition);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    padding: 2rem;
}

.app-container {
    width: 100%;
    max-width: 1200px;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

/* Header */
header {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    padding-bottom: 1rem;
    border-bottom: 2px solid var(--accent-color);
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: -0.05em;
    line-height: 1;
    margin-bottom: 0.25rem;
}

#current-date-header {
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-weight: 500;
}

#theme-toggle {
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background var(--transition);
}

#theme-toggle:hover {
    background-color: var(--border-color);
}

/* Grid Layout */
.grid-layout {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-auto-rows: minmax(300px, auto);
    gap: 1.5rem;
}

@media (max-width: 1100px) {
    .grid-layout {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .grid-layout {
        grid-template-columns: 1fr;
    }
    .span-3, .span-2 {
        grid-column: span 1 !important;
    }
}

.span-2 { grid-column: span 2; }
.span-3 { grid-column: span 3; }

@media (max-width: 900px) {
    .grid-layout {
        grid-template-columns: 1fr;
    }
    .span-2 {
        grid-column: span 1;
    }
}

.span-2 {
    grid-column: span 2;
}

/* Widgets */
.widget {
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    transition: border-color var(--transition), box-shadow var(--transition);
}

.widget:hover {
    border-color: var(--text-secondary);
    box-shadow: var(--shadow-md);
}

.widget-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.widget-header h2 {
    font-size: 1.1rem;
    font-weight: 600;
    letter-spacing: -0.02em;
}

.widget-content {
    padding: 1.5rem;
    flex-grow: 1;
    display: flex;
}

.flex-col {
    flex-direction: column;
    gap: 1rem;
}

.center-content {
    align-items: center;
    justify-content: center;
}

/* Forms & Inputs */
.input-group,
.input-group-multi {
    display: flex;
    gap: 0.5rem;
    width: 100%;
}

.input-group-multi {
    flex-direction: column;
}

.row {
    display: flex;
    gap: 0.5rem;
}

input[type="text"],
input[type="date"] {
    flex-grow: 1;
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background-color: transparent;
    color: var(--text-primary);
    font-family: inherit;
    font-size: 0.95rem;
    transition: border-color var(--transition);
}

input:focus, textarea:focus {
    outline: none;
    border-color: var(--accent-color);
}

/* Buttons */
button {
    font-family: inherit;
    font-weight: 500;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: all var(--transition);
    border: none;
}

.btn-primary {
    background-color: var(--accent-color);
    color: var(--accent-text);
    padding: 0.75rem 1.25rem;
}

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

.btn-secondary {
    background-color: transparent;
    color: var(--text-primary);
    padding: 0.75rem 1.25rem;
    border: 1px solid var(--border-color);
}

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

.btn-icon, .delete-btn {
    background: transparent;
    border: none;
    color: var(--text-secondary);
    padding: 0.5rem;
    cursor: pointer;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
}

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

.delete-btn:hover {
    color: var(--danger-color);
    background-color: rgba(255, 0, 0, 0.1);
}

/* Lists */
.scrollable-list {
    list-style: none;
    overflow-y: auto;
    max-height: 250px;
    padding-right: 0.5rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

/* Custom Scrollbar for list */
.scrollable-list::-webkit-scrollbar {
    width: 4px;
}
.scrollable-list::-webkit-scrollbar-thumb {
    background-color: var(--border-color);
    border-radius: var(--radius-sm);
}

.list-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background-color: transparent;
    animation: slideIn 0.3s ease-out forwards;
    transition: border-color var(--transition);
}

.list-item:hover {
    border-color: var(--text-secondary);
}

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

/* Task Specific */
.task-content {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    flex-grow: 1;
}

.task-checkbox {
    appearance: none;
    width: 1.25rem;
    height: 1.25rem;
    border: 2px solid var(--text-secondary);
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
}

.task-checkbox:checked {
    background-color: var(--accent-color);
    border-color: var(--accent-color);
}

.task-checkbox:checked::after {
    content: "✓";
    color: var(--accent-text);
    font-size: 0.8rem;
    font-weight: bold;
}

.list-item.completed .task-text {
    text-decoration: line-through;
    color: var(--text-secondary);
}

/* Exam Specific */
.exam-info {
    display: flex;
    flex-direction: column;
}

.exam-title {
    font-weight: 600;
}

.exam-meta {
    font-size: 0.8rem;
    color: var(--text-secondary);
    display: flex;
    gap: 0.5rem;
}
.exam-meta strong {
    color: var(--text-primary);
    font-weight: 500;
}

.exam-urgent {
    border-left: 3px solid var(--danger-color);
}

/* Timer Specific */
.timer-modes {
    display: flex;
    justify-content: center;
    gap: 0.5rem;
    padding: 1rem;
    border-bottom: 1px solid var(--border-color);
    background-color: transparent;
}

.mode-btn {
    background: transparent;
    border: none;
    color: var(--text-secondary);
    padding: 0.4rem 0.8rem;
    font-size: 0.85rem;
    font-weight: 600;
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition);
}

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

.mode-btn.active {
    background-color: var(--accent-color);
    color: var(--accent-text);
}

.timer-display {
    font-size: 4rem;
    font-weight: 700;
    font-variant-numeric: tabular-nums;
    letter-spacing: -0.05em;
    margin-bottom: 1.5rem;
    line-height: 1;
}

.timer-controls {
    display: flex;
    gap: 1rem;
}

/* Notes Specific */
.notes-textarea {
    width: 100%;
    height: 100%;
    min-height: 200px;
    border: none;
    resize: none;
    padding: 1.5rem;
    background-color: transparent;
    color: var(--text-primary);
    font-family: inherit;
    font-size: 0.95rem;
    line-height: 1.6;
}
.notes-textarea:focus {
    outline: none;
}

/* Resources Specific */
.resource-link {
    color: var(--accent-color);
    text-decoration: none;
    font-weight: 500;
    word-break: break-all;
}
.resource-link:hover {
    text-decoration: underline;
}

/* Calendar Specific */
.calendar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 1.5rem;
}

.calendar-header h2 {
    font-size: 1.1rem;
    font-weight: 600;
}

.calendar-days-names {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    text-align: center;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.calendar-grid {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    grid-template-rows: repeat(6, 1fr);
    gap: 2px;
    height: 100%;
}

.calendar-day {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: flex-start;
    padding: 0.5rem 0.25rem;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    position: relative;
}

.calendar-day:hover:not(.empty) {
    background-color: var(--border-color);
    transform: scale(1.05);
}

.calendar-day.empty {
    color: var(--border-color);
}

.calendar-day.today {
    background-color: var(--accent-color);
    color: var(--accent-text);
    font-weight: bold;
}

.calendar-indicators {
    display: flex;
    gap: 3px;
    margin-top: 4px;
}

.indicator {
    width: 6px;
    height: 6px;
    border-radius: 50%;
}

.indicator.exam {
    background-color: var(--danger-color);
}

.indicator.task {
    background-color: var(--text-secondary);
}

.indicator.reminder {
    background-color: #8b5cf6; /* A distinct purple for reminders */
}

.calendar-day.today .indicator.exam,
.calendar-day.today .indicator.task,
.calendar-day.today .indicator.reminder {
    border: 1px solid var(--surface-color);
}

/* Tracking Banner & Path */
.tracking-banner {
    width: 100%;
    padding: 0.5rem 1rem;
    background-color: var(--accent-color);
    color: var(--accent-text);
    border-radius: var(--radius-sm);
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-weight: 600;
    margin-bottom: 0.5rem;
}
.tracking-banner.hidden {
    display: none;
}
.tracking-banner .btn-icon {
    color: var(--accent-text);
}
.tracking-banner .btn-icon:hover {
    background-color: rgba(255,255,255,0.2);
}

.tracked-path {
    background-color: rgba(0, 0, 0, 0.05); /* very light path */
    border-radius: 0;
}
body.dark-mode .tracked-path {
    background-color: rgba(255, 255, 255, 0.05);
}

.tracked-target {
    border: 2px solid var(--accent-color);
    background-color: rgba(0, 0, 0, 0.1);
}
body.dark-mode .tracked-target {
    background-color: rgba(255, 255, 255, 0.1);
}

/* Base Modal (for Reminders) */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 500;
    display: flex;
    align-items: center;
    justify-content: center;
}
.modal.hidden {
    display: none;
}
.modal-content {
    width: 100%;
    max-width: 400px;
}

/* PDF Modal Specifics */
.pdf-modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background-color: var(--bg-color);
    z-index: 1000;
    display: flex;
    flex-direction: column;
}

.pdf-modal.hidden {
    display: none;
}

.pdf-toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    background-color: var(--surface-color);
    border-bottom: 2px solid var(--accent-color);
    box-shadow: var(--shadow-sm);
}

.pdf-toolbar-group {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.pdf-title {
    font-weight: 600;
    font-size: 1.1rem;
}

.pdf-page-info {
    font-size: 0.9rem;
    font-weight: 500;
    min-width: 100px;
    text-align: center;
}

.pdf-viewer-container {
    flex-grow: 1;
    overflow-y: auto;
    overflow-x: auto;
    display: flex;
    justify-content: center;
    padding: 2rem;
    background-color: var(--border-color); /* slightly darker bg for contrast */
}

body.dark-mode .pdf-viewer-container {
    background-color: #1a1a1a;
}

.canvas-wrapper {
    position: relative;
    box-shadow: var(--shadow-lg);
    background-color: white; /* PDF should always have a white backboard */
    /* Dimensions will be set via JS based on PDF aspect ratio */
}

canvas {
    display: block;
}

#pdf-render-canvas {
    position: absolute;
    top: 0;
    left: 0;
    z-index: 1;
}

#pdf-draw-canvas {
    position: absolute;
    top: 0;
    left: 0;
    z-index: 2;
    cursor: crosshair;
}