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

:root {
    --primary-color: #007bff;
    --primary-hover: #0056b3;
    --text-color: #333;
    --border-color: #ddd;
    --bg-color: #f8f9fa;
    --spacing-unit: 1rem;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

.container {
    width: 100%;
    max-width: 100%;
    padding: var(--spacing-unit);
    margin: 0 auto;
}

header {
    text-align: center;
    margin-bottom: 2rem;
    padding: var(--spacing-unit) 0;
    border-bottom: 2px solid var(--primary-color);
}

header h1 {
    font-size: 1.75rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

main {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

section {
    background: white;
    padding: var(--spacing-unit);
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

section h2 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-unit);
    color: var(--primary-color);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-bottom: var(--spacing-unit);
}

label {
    font-weight: 600;
    font-size: 0.95rem;
}

input[type="file"],
select {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    font-size: 1rem;
    font-family: inherit;
    width: 100%;
}

input[type="file"]:focus,
select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.25);
}

.status-message {
    padding: 0.75rem;
    border-radius: 4px;
    margin-top: 0.5rem;
    display: none;
}

.status-message.show {
    display: block;
}

.status-message.success {
    background-color: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

.status-message.error {
    background-color: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

.status-message.info {
    background-color: #d1ecf1;
    color: #0c5460;
    border: 1px solid #bee5eb;
}

/* Stops Container */
.stops-container {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.stop-card {
    background: #f9f9f9;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 1rem;
    margin-bottom: 1rem;
}

.stop-header {
    font-weight: 700;
    font-size: 1.05rem;
    margin-bottom: 1rem;
    color: var(--text-color);
}

.stop-control-group {
    margin-bottom: 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.control-label {
    font-weight: 600;
    font-size: 0.9rem;
    color: #555;
}

.slider-values {
    font-size: 0.95rem;
    color: #333;
    font-weight: 600;
}

.range-slider {
    position: relative;
    width: 100%;
    height: 3rem;
    cursor: pointer;
}

.range-slider input {
    position: absolute;
    left: 0;
    top: 0.8rem;
    width: 100%;
    background: transparent;
    pointer-events: none;
    -webkit-appearance: none;
    appearance: none;
    height: 2rem;
}

.range-slider input:hover {
    cursor: pointer;
}

.range-slider input::-webkit-slider-runnable-track {
    height: 8px;
    border-radius: 999px;
    background: #ddd;
}

.range-slider input::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: var(--primary-color);
    border: 2px solid white;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.2);
    cursor: pointer;
    margin-top: -7px;
}

.range-slider input::-moz-range-track {
    height: 8px;
    border-radius: 999px;
    background: #ddd;
}

.range-slider input::-moz-range-thumb {
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: var(--primary-color);
    border: 2px solid white;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.2);
    cursor: pointer;
}

.range-slider input[data-handle="high"] {
    z-index: 2;
    opacity: 0.85;
}

.range-slider input[data-handle="low"] {
    z-index: 1;
    opacity: 0.85;
}

.slider-value {
    min-width: 60px;
    text-align: left;
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--primary-color);
}

.holding-policy-group {
    margin-top: 1rem;
}

.policy-label {
    font-weight: 600;
    font-size: 0.9rem;
    color: #555;
    margin-bottom: 0.5rem;
    display: block;
}

.policy-options {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.policy-checkbox {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
}

input[type="checkbox"] {
    width: 18px;
    height: 18px;
    cursor: pointer;
    accent-color: var(--primary-color);
}

.dynamic-holding-slider {
    width: 50%;
    margin-left: 0;
    margin-top: 1rem;
}

@media (max-width: 620px) {
    .dynamic-holding-slider {
        width: 100%;
    }
}

.policy-checkbox label {
    margin: 0;
    font-weight: 400;
    cursor: pointer;
    flex: 1;
}

/* Buttons */
.btn-primary {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 1rem;
    border-radius: 6px;
    font-size: 1.05rem;
    font-weight: 600;
    cursor: pointer;
    width: 100%;
    transition: background-color 0.3s ease;
}

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

.btn-primary:active {
    transform: scale(0.98);
}

.btn-primary:disabled {
    background-color: #ccc;
    cursor: not-allowed;
    transform: none;
}

/* Chart Container */
.chart-container {
    position: relative;
    width: 100%;
    height: auto;
    margin-top: 1rem;
}

.chart-container canvas {
    max-height: 800px;
}

/* Tablet and Desktop Adjustments */
@media (min-width: 768px) {
    .container {
        max-width: 900px;
    }

    header h1 {
        font-size: 2rem;
    }

    section h2 {
        font-size: 1.5rem;
    }

    .chart-container canvas {
        max-height: 1200px;
    }
}

/* Loading spinner */
.spinner {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(0, 123, 255, 0.3);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}