:root {
    --primary-color: #2c3e50;
    --secondary-color: #3498db;
    --accent-color: #27ae60;
    --bg-color: #f4f7f9;
    --card-bg-color: #ffffff;
    --font-color: #333;
    --border-color: #dfe6e9;
    --navbar-bg: #2c3e50;
    --navbar-link-color: white;
}

[data-theme="dark"] {
    --primary-color: #ecf0f1;
    --secondary-color: #3498db;
    --accent-color: #2ecc71;
    --bg-color: #2c3e50;
    --card-bg-color: #34495e;
    --font-color: #ecf0f1;
    --border-color: #4a6278;
    --navbar-bg: #1f2a36;
}


body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--font-color);
    margin: 0;
    padding: 0;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: background-color 0.3s, color 0.3s;
}

.navbar {
    width: 100%;
    background-color: var(--navbar-bg);
    padding: 10px 20px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-sizing: border-box;
}

.nav-right {
    display: flex;
    align-items: center;
    gap: 15px;
}

.nav-link {
    color: var(--navbar-link-color);
    text-decoration: none;
    font-weight: 500;
    padding: 5px 10px;
    border-radius: 4px;
    transition: background-color 0.3s;
}

.nav-link:hover {
    background-color: rgba(255, 255, 255, 0.2);
}

.theme-toggle-btn {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--navbar-link-color);
    padding: 5px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
}

.theme-toggle-btn:hover {
    background-color: rgba(255, 255, 255, 0.2);
}

.theme-toggle-btn .feather-sun { display: block; }
.theme-toggle-btn .feather-moon { display: none; }

[data-theme="dark"] .theme-toggle-btn .feather-sun { display: none; }
[data-theme="dark"] .theme-toggle-btn .feather-moon { display: block; }

.container {
    width: 100%;
    max-width: 1000px;
    background-color: var(--card-bg-color);
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.1);
    transition: background-color 0.3s;
    margin: 20px auto;
    box-sizing: border-box;
    flex-grow: 1;
}

h1, h2, h3 {
    text-align: center;
    color: var(--primary-color);
}

h1 { margin-bottom: 15px; }
h2 { margin-top: 20px; margin-bottom: 25px; font-size: 1.8em; border-bottom: 2px solid var(--border-color); padding-bottom: 15px; }
h3 { text-align: left; }

#selection-screen { text-align: center; }
#selection-screen p { font-size: 1.1em; margin-bottom: 30px; }
.selection-buttons { display: flex; gap: 20px; justify-content: center; flex-wrap: wrap; }
.mode-button { padding: 15px 30px; font-size: 1.1em; font-weight: bold; border: none; border-radius: 8px; cursor: pointer; transition: transform 0.2s, box-shadow 0.2s; color: white; min-width: 250px; }
.mode-button:hover { transform: translateY(-3px); box-shadow: 0 6px 15px rgba(0, 0, 0, 0.15); }

#compare-sources-btn { background-color: var(--secondary-color); }
#compare-tippers-btn { background-color: #e67e22; }

#calculator-container { animation: fadeIn 0.5s; }
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.table-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 20px;
}

.add-column-button {
    padding: 8px 16px;
    font-size: 0.9em;
    font-weight: bold;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    color: white;
    background-color: #9b59b6;
    transition: background-color 0.3s;
    margin-left: auto; 
}

.add-column-button:hover {
    background-color: #8e44ad;
}
.table-wrapper {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 15px;
    font-size: 0.95em;
}

th, td {
    border: 1px solid var(--border-color);
    padding: 12px;
    text-align: left;
    vertical-align: middle;
}

thead th {
    background-color: #ecf0f1;
    font-weight: bold;
    text-align: center;
    color: #333;
}
[data-theme="dark"] thead th { background-color: #4a6278; color: var(--font-color); }


tbody td:first-child {
    font-weight: 500;
    white-space: nowrap;
}

input[type="number"] {
    width: 100%;
    padding: 8px;
    border: 1px solid #ccc;
    border-radius: 4px;
    box-sizing: border-box;
    font-size: 1em;
    text-align: right;
    background-color: var(--card-bg-color);
    color: var(--font-color);
}
[data-theme="dark"] input[type="number"] { border-color: var(--border-color); }

.controls { display: flex; gap: 15px; margin-top: 30px; flex-wrap: wrap; }
.control-button { flex-grow: 1; padding: 12px; font-size: 1.1em; font-weight: bold; border: none; border-radius: 5px; cursor: pointer; transition: background-color 0.3s; color: white; min-width: 150px; }

#calculate-btn { background-color: var(--accent-color); }
#back-btn { background-color: #7f8c8d; }

#results-table span { font-weight: bold; font-size: 1.1em; display: block; text-align: right; }
#summary-row td { text-align: center; font-size: 1.1em; font-weight: bold; background-color: #e8f6ef; color: var(--accent-color); }
[data-theme="dark"] #summary-row td { background-color: #2c3e50; }
        
.hidden { display: none; }

.footer { text-align: center; margin-top: 20px; padding: 20px; color: #7f8c8d; font-size: 0.9em; background-color: var(--bg-color); }
[data-theme="dark"] .footer { color: #bdc3c7; }

@media (max-width: 768px) {
    body { padding: 0; }
    .container { padding: 15px; margin: 0; border-radius: 0; box-shadow: none; }
    h1 { font-size: 1.6em; }
    h2 { font-size: 1.3em; }
    .selection-buttons { flex-direction: column; }
    .mode-button { min-width: unset; width: 100%; }
    th, td { padding: 8px; font-size: 0.9em; }
    .controls { flex-direction: column; }
    .nav-link { font-size: 0.9em; }
    
    #input-table tbody td:first-child,
    #results-table tbody td:first-child {
        white-space: normal;
        min-width: 100px;
    }
}