:root {
    --page-bg: #f9fafb;
    --card-bg: #ffffff;
    --text-color: #1f2937;
    --border-color: #e5e7eb;
    --input-bg: #f9fafb;
    --theme-switch-bg-off: #d1d5db;
    --theme-switch-bg-on: #3b82f6;
    --button-primary-bg: #3b82f6;
    --button-primary-text: #ffffff;
    --button-secondary-bg: #e5e7eb;
    --button-secondary-text: #374151;
    --toast-bg: #1f2937;
    --toast-text: #f8fafc;
}

[data-theme="dark"] {
    --page-bg: #0f172a;
    --card-bg: #1e293b;
    --text-color: #f8fafc;
    --border-color: #334155;
    --input-bg: #334155;
    --button-secondary-bg: #334155;
    --button-secondary-text: #f8fafc;
}

/* --- Base & Layout --- */
* { box-sizing: border-box; }
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--page-bg);
    color: var(--text-color);
    margin: 0;
    transition: background-color 0.3s, color 0.3s;
}
.main-container {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
    padding: 2rem;
    max-width: 1400px;
    margin: 0 auto;
}
@media (min-width: 1024px) {
    .main-container { grid-template-columns: 1fr 1fr; }
    .chart-card-container { position: sticky; top: 2rem; align-self: start; }
}

/* --- Header --- */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    background-color: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    transition: background-color 0.3s, border-color 0.3s;
}
.header__title h1 { margin: 0; font-size: 1.5rem; }
.header__title p { margin: 0; color: #6b7280; }

/* --- Theme Switcher --- */
.theme-switcher { display: flex; align-items: center; gap: 0.75rem; }
.theme-switch {
    position: relative;
    display: inline-block;
    width: 44px;
    height: 24px;
    cursor: pointer;
}
.theme-switch input { opacity: 0; width: 0; height: 0; }
.slider-track {
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background-color: var(--theme-switch-bg-off);
    border-radius: 34px;
    transition: background-color 0.4s;
}
.slider-track:before {
    position: absolute;
    content: "";
    height: 18px;
    width: 18px;
    left: 3px;
    bottom: 3px;
    background-color: white;
    border-radius: 50%;
    transition: transform 0.4s;
}
.theme-switch input:checked + .slider-track {
    background-color: var(--theme-switch-bg-on);
}
.theme-switch input:checked + .slider-track:before {
    transform: translateX(20px);
}

/* --- Cards --- */
.card {
    background-color: var(--card-bg);
    border-radius: 0.75rem;
    border: 1px solid var(--border-color);
    padding: 1.5rem;
    transition: background-color 0.3s, border-color 0.3s;
}
.chart-card { 
    display: flex; 
    justify-content: center; 
    align-items: center; 
}
#chartCanvas { background-color: #ffffff; border-radius: 0.5rem; }


/* --- Controls --- */
.controls-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 1.5rem; }
.controls-header h2 { margin: 0; }
.mode-toggle { display: flex; align-items: center; gap: 0.5rem; }
.switch { position: relative; display: inline-block; width: 50px; height: 24px; }
.switch input { opacity: 0; width: 0; height: 0; }
.slider { position: absolute; cursor: pointer; top: 0; left: 0; right: 0; bottom: 0; background-color: #ccc; transition: .4s; }
.slider:before { position: absolute; content: ""; height: 18px; width: 18px; left: 3px; bottom: 3px; background-color: white; transition: .4s; }
input:checked + .slider { background-color: var(--theme-switch-bg-on); }
input:checked + .slider:before { transform: translateX(26px); }
.slider.round { border-radius: 34px; }
.slider.round:before { border-radius: 50%; }

.control-group { margin-bottom: 1.5rem; }
.control-group label { display: block; font-weight: 500; margin-bottom: 0.5rem; }
input[type="number"], input[type="text"], select {
    width: 100%;
    padding: 0.5rem 0.75rem;
    border-radius: 0.375rem;
    border: 1px solid var(--border-color);
    background-color: var(--input-bg);
    color: var(--text-color);
    font-size: 1rem;
}
.grid-2-col { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; }
.color-control-grid { display: grid; grid-template-columns: auto 1fr; align-items: center; gap: 0.5rem 1rem; }
.grid-3-col { display: grid; grid-template-columns: 1fr 1fr auto; gap: 1rem; align-items: center; }

.inline-checkbox-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-top: 0.75rem;
}
.inline-checkbox-group label {
    margin-bottom: 0;
    font-weight: normal;
}

/* --- Color Picker Component --- */
.color-picker-wrapper { display: flex; align-items: center; gap: 0.5rem; }
.color-hex-input { width: 80px; }
.color-swatch {
    width: 28px; height: 28px;
    border: 2px solid var(--border-color);
    border-radius: 0.375rem;
    cursor: pointer;
}
.palette-toggle-btn {
    background: none; border: none; font-size: 1.5rem; cursor: pointer; color: var(--text-color); padding: 0;
}
#colorPalette {
    position: absolute;
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 0.5rem;
    padding: 0.75rem;
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 0.5rem;
    box-shadow: 0 10px 15px -3px rgba(0,0,0,0.1);
    z-index: 100;
}
.palette-color {
    width: 24px; height: 24px; border-radius: 50%; cursor: pointer;
    border: 1px solid rgba(0,0,0,0.1);
}

/* --- Dynamic Segments --- */
.segment-item {
    display: grid;
    grid-template-columns: 1fr 1fr auto auto;
    gap: 0.5rem;
    align-items: center;
    padding: 0.75rem;
    border: 1px dashed var(--border-color);
    border-radius: 0.5rem;
    margin-bottom: 1rem;
}
.remove-segment-btn {
    background: none; border: none; color: #ef4444; font-size: 1.5rem; cursor: pointer; padding: 0.25rem;
}

/* --- Buttons & Footer --- */
.button-primary {
    width: 100%;
    padding: 0.75rem 1rem;
    background-color: var(--button-primary-bg);
    color: var(--button-primary-text);
    border: none;
    border-radius: 0.375rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
}
.controls-footer {
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}
.export-options { display: flex; align-items: center; gap: 0.5rem; margin-bottom: 1rem; }
.button-group { display: flex; gap: 1rem; }
.button-group button {
    flex: 1;
    padding: 0.6rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: 0.375rem;
    background-color: var(--button-secondary-bg);
    color: var(--button-secondary-text);
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 500;
}

/* --- Chart SVG Elements --- */
.chart-arc { transition: stroke-dashoffset 1s ease-in-out; }
.chart-text { transition: font-size 0.3s, fill 0.3s; }
.outer-label { 
    transition: font-size 0.3s, fill 0.3s;
}

/* --- Toast Notification --- */
.toast {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background-color: var(--toast-bg);
    color: var(--toast-text);
    padding: 1rem 1.5rem;
    border-radius: 0.5rem;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    opacity: 0;
    visibility: hidden;
    transition: transform 0.4s ease, opacity 0.4s ease, visibility 0.4s;
    z-index: 1000;
}
.toast.show {
    transform: translateX(-50%) translateY(0);
    opacity: 1;
    visibility: visible;
}