:root {
    --bg-dark: #121212;
    --bg-card: #1e1e1e;
    --text-light: #e0e0e0;
    --text-subtle: #888;
    --color-primary: #007bff; /* Blue */
    --color-danger: #dc3545; /* Red */
    --color-accent: #28a745; /* Green Accent */
    --color-physics: #4A90E2; 
    --color-chemistry: #F5A623;
    --color-math: #50E3C2;
    --color-biology: #7ED321;
    --color-bangla: #FF5733;
    --color-english: #9013FE;
    --color-gk: #FFC300;
}

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

body {
    font-family: 'Poppins', sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-light);
    min-height: 100vh;
    padding: 20px;
}

/* --- Dashboard Layout --- */
.dashboard-container {
    display: flex;
    gap: 30px;
    max-width: 1400px;
    margin: 0 auto;
}

.sidebar {
    width: 300px;
    padding: 20px;
    background-color: var(--bg-card);
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.5);
}

.main-content {
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    gap: 30px;
}

/* --- Typography & Headings --- */
h1 { font-weight: 700; font-size: 2.2rem; }
h2 { font-weight: 500; font-size: 1.5rem; margin-bottom: 20px; border-bottom: 1px solid var(--bg-dark); padding-bottom: 10px; }
h3 { font-weight: 500; font-size: 1.2rem; margin-bottom: 15px; }

/* --- Subject Grid & Cards --- */
.subject-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 15px;
    margin-bottom: 30px;
}

.subject-card {
    background-color: var(--bg-dark);
    padding: 15px;
    border-radius: 8px;
    border-left: 5px solid var(--color-primary); /* Default border, overridden by JS */
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.subject-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 15px rgba(0, 0, 0, 0.4);
}

.subject-card.selected {
    outline: 2px solid var(--color-accent);
    box-shadow: 0 0 10px var(--color-accent);
}

.subject-info strong {
    font-size: 1.1rem;
    display: block;
    margin-bottom: 5px;
}

.subject-info small {
    color: var(--text-subtle);
}

/* --- Timer Card --- */
.timer-card {
    background-color: var(--bg-card);
    padding: 40px;
    border-radius: 12px;
    text-align: center;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.5);
}

#active-subject {
    color: var(--color-accent);
    margin-bottom: 30px;
}

.timer-display {
    font-size: 2rem;
    font-weight: 300;
    letter-spacing: 5px;
    color: var(--text-light);
    margin-bottom: 40px;
}

/* --- Timer Controls --- */
.timer-controls {
    display: flex;
    justify-content: center;
    gap: 20px;
}

.control-btn {
    padding: 15px 30px;
    font-size: 1.1rem;
    font-weight: 500;
    border: none;
    border-radius: 50px;
    cursor: pointer;
    transition: background-color 0.3s, transform 0.1s;
}

.control-btn.primary {
    background-color: var(--color-accent);
    color: var(--bg-dark);
}
.control-btn.primary:hover:not(:disabled) {
    background-color: #38c172;
}

.control-btn.danger {
    background-color: var(--color-danger);
    color: white;
}
.control-btn.danger:hover:not(:disabled) {
    background-color: #c82333;
}

.control-btn:disabled {
    background-color: var(--text-subtle);
    cursor: not-allowed;
    opacity: 0.6;
}

/* --- History Section --- */
.history-section {
    padding: 20px;
    background-color: var(--bg-card);
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.5);
}

.session-log {
    max-height: 250px;
    overflow-y: auto;
    padding-right: 10px; /* Space for scrollbar */
}

.log-entry {
    background-color: var(--bg-dark);
    padding: 10px 15px;
    border-radius: 5px;
    margin-bottom: 8px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.log-subject {
    font-weight: 700;
}

.log-duration {
    color: var(--color-accent);
}

/* --- Responsive Adjustments --- */
@media (max-width: 1000px) {
    .dashboard-container {
        flex-direction: column;
    }
    .sidebar {
        width: 100%;
    }
    .subject-grid {
        grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    }
}