/* ====================
   CSS Custom Properties
   ==================== */
:root {
    /* Colors */
    --color-primary: #4A90E2;
    --color-primary-hover: #3a7bc8;
    --color-secondary: #50C878;
    --color-border: #ccc;
    --color-background: #ffffff;
    --color-text: #333333;
    --color-bg-alt: #f5f5f5;
    --color-error: #f44336;

    /* Spacing */
    --spacing-xs: 5px;
    --spacing-sm: 10px;
    --spacing-md: 20px;
    --spacing-lg: 30px;
    --spacing-xl: 40px;

    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto,
        'Helvetica Neue', Arial, sans-serif;
    --font-size-base: 16px;
    --font-size-lg: 18px;
    --line-height: 1.6;

    /* Borders */
    --border-radius: 8px;
    --border-radius-sm: 4px;
    --border-width: 1px;

    /* Transitions */
    --transition-speed: 0.3s;
}

/* ====================
   Base Styles
   ==================== */
* {
    box-sizing: border-box;
}

body {
    font-family: var(--font-family);
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-md);
    color: var(--color-text);
    line-height: var(--line-height);
    font-size: var(--font-size-base);
}

/* ====================
   Accessibility
   ==================== */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--color-primary);
    color: white;
    padding: 8px;
    text-decoration: none;
    z-index: 100;
}

.skip-link:focus {
    top: 0;
}

/* Focus visible for keyboard navigation */
*:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* ====================
   Typography
   ==================== */
h1,
h2,
h3 {
    margin-top: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
}

h1 {
    font-size: 2rem;
}

h2 {
    font-size: 1.5rem;
}

h3,
legend {
    font-size: 1.25rem;
}

/* ====================
   Layout
   ==================== */
header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

header img {
    display: block;
    margin: 0 auto var(--spacing-md);
}

main {
    margin-bottom: var(--spacing-xl);
}

section {
    margin-bottom: var(--spacing-xl);
}

footer {
    text-align: center;
    padding: var(--spacing-lg) 0;
    border-top: 1px solid var(--color-border);
}

/* ====================
   Forms
   ==================== */
fieldset {
    border: none;
    padding: 0;
    margin: var(--spacing-lg) 0;
}

legend {
    font-weight: bold;
    padding: 0;
    margin-bottom: var(--spacing-md);
}

/* Form field styles */
.field {
    margin: var(--spacing-md) 0;
    display: flex;
    align-items: flex-start;
    padding: var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    transition: background-color var(--transition-speed);
}

.field:hover {
    background-color: var(--color-bg-alt);
}

.field input[type="number"] {
    margin-right: var(--spacing-md);
    width: 60px;
    padding: 8px;
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--border-radius-sm);
    font-size: var(--font-size-base);
    font-family: var(--font-family);
}

.field input[type="number"]:focus {
    outline: 2px solid var(--color-primary);
    border-color: var(--color-primary);
}

.field label {
    flex: 1;
}

/* Number input styling - remove default spinners for better control */
input[type="number"] {
    appearance: textfield;
    -moz-appearance: textfield;
}

input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
    opacity: 1;
}

/* Text inputs */
input[type="text"] {
    padding: 10px;
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--border-radius-sm);
    font-size: var(--font-size-base);
    font-family: var(--font-family);
    width: 100%;
    max-width: 400px;
}

input[type="text"]:focus {
    outline: 2px solid var(--color-primary);
    border-color: var(--color-primary);
}

/* ====================
   Buttons
   ==================== */
.btn-group {
    display: flex;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

button {
    padding: 12px 24px;
    cursor: pointer;
    background-color: var(--color-primary);
    color: white;
    border: none;
    border-radius: var(--border-radius-sm);
    font-size: var(--font-size-base);
    font-family: var(--font-family);
    font-weight: 500;
    transition: all var(--transition-speed) ease;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

button:hover {
    background-color: var(--color-primary-hover);
    transform: translateY(-1px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
}

button:active {
    transform: translateY(0);
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
}

button:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

button:disabled {
    background-color: var(--color-border);
    cursor: not-allowed;
    transform: none;
}

/* ====================
   Chart Container
   ==================== */
.chart-container {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-md);
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--border-radius);
    background-color: var(--color-background);
    width: 100%;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
    height: 500px;
    position: relative;
}

/* ====================
   Error Messages
   ==================== */
.error-message {
    padding: var(--spacing-sm) var(--spacing-md);
    margin: var(--spacing-sm) 0;
    background-color: var(--color-error);
    color: white;
    border-radius: var(--border-radius-sm);
    font-weight: 500;
}

/* ====================
   Responsive Design
   ==================== */
@media (max-width: 768px) {
    body {
        padding: var(--spacing-sm);
    }

    .chart-container {
        height: 400px;
        padding: var(--spacing-sm);
    }

    .field {
        flex-direction: column;
        align-items: flex-start;
    }

    .field input[type="number"] {
        margin-bottom: var(--spacing-sm);
    }

    h1 {
        font-size: 1.5rem;
    }

    h2 {
        font-size: 1.25rem;
    }

    header img {
        width: 100px;
        height: 100px;
    }
}

@media (min-width: 769px) and (max-width: 1024px) {
    .chart-container {
        height: 550px;
    }
}

@media (min-width: 1025px) {
    body {
        padding: var(--spacing-xl);
    }

    .chart-container {
        height: 600px;
        padding: var(--spacing-lg);
    }
}

/* ====================
   Print Styles
   ==================== */
@media print {

    .btn-group,
    .skip-link {
        display: none;
    }

    .chart-container {
        page-break-inside: avoid;
        border: 1px solid #000;
    }

    body {
        max-width: 100%;
        padding: 0;
    }

    header,
    section {
        page-break-inside: avoid;
    }
}

/* ====================
   Animations
   ==================== */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.field {
    animation: fadeIn 0.3s ease-in-out;
}

/* ====================
   Utility Classes
   ==================== */
.text-center {
    text-align: center;
}

.mt-lg {
    margin-top: var(--spacing-lg);
}

.mb-lg {
    margin-bottom: var(--spacing-lg);
}