/* ===== CSS Variables ===== */
:root {
    --ev-primary: #10b981;
    --ev-light: #d1fae5;
    --ev-dark: #059669;
    --gas-primary: #3b82f6;
    --gas-light: #dbeafe;
    --gas-dark: #2563eb;
    --bg-gradient-start: #0f172a;
    --bg-gradient-end: #1e3a5f;
    --card-bg: rgba(255, 255, 255, 0.95);
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: linear-gradient(135deg, var(--bg-gradient-start) 0%, var(--bg-gradient-end) 50%, #134e4a 100%);
    min-height: 100vh;
    overflow-x: hidden;
}

.bg-decoration { position: fixed; top: 0; left: 0; width: 100%; height: 100%; pointer-events: none; z-index: 0; overflow: hidden; }
.bg-circle { position: absolute; border-radius: 50%; filter: blur(80px); opacity: 0.4; }
.bg-circle-1 { width: 600px; height: 600px; background: radial-gradient(circle, var(--ev-primary), transparent); top: -200px; right: -100px; animation: float1 20s ease-in-out infinite; }
.bg-circle-2 { width: 500px; height: 500px; background: radial-gradient(circle, var(--gas-primary), transparent); bottom: -150px; left: -100px; animation: float2 25s ease-in-out infinite; }
.bg-circle-3 { width: 400px; height: 400px; background: radial-gradient(circle, #8b5cf6, transparent); top: 50%; left: 50%; transform: translate(-50%, -50%); animation: float3 30s ease-in-out infinite; }

@keyframes float1 { 0%, 100% { transform: translate(0, 0) scale(1); } 50% { transform: translate(-50px, 50px) scale(1.1); } }
@keyframes float2 { 0%, 100% { transform: translate(0, 0) scale(1); } 50% { transform: translate(50px, -30px) scale(1.05); } }
@keyframes float3 { 0%, 100% { transform: translate(-50%, -50%) scale(1); } 50% { transform: translate(-50%, -50%) scale(1.15); } }

.container { position: relative; z-index: 1; max-width: 1200px; margin: 0 auto; padding: 20px; }
.header { text-align: center; padding: 40px 20px; color: white; }
.logo { display: flex; align-items: center; justify-content: center; gap: 16px; margin-bottom: 16px; }
.logo-icon { width: 56px; height: 56px; filter: drop-shadow(0 4px 6px rgba(0, 0, 0, 0.2)); }
.header h1 { font-size: 2.5rem; font-weight: 700; background: linear-gradient(135deg, #fff 0%, var(--ev-light) 50%, var(--gas-light) 100%); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.subtitle { font-size: 1.2rem; color: rgba(255, 255, 255, 0.8); margin-top: 8px; }

.calculator-section { background: var(--card-bg); border-radius: var(--radius-xl); padding: 32px; box-shadow: var(--shadow-xl); margin-bottom: 32px; }
.calculator-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; margin-bottom: 24px; }
@media (max-width: 768px) { .calculator-grid { grid-template-columns: 1fr; } }

.calc-card { border-radius: var(--radius-lg); overflow: hidden; box-shadow: var(--shadow-md); transition: transform var(--transition-normal), box-shadow var(--transition-normal); }
.calc-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.card-header { padding: 16px 20px; display: flex; align-items: center; gap: 12px; color: white; }
.ev-header { background: linear-gradient(135deg, var(--ev-primary), var(--ev-dark)); }
.gas-header { background: linear-gradient(135deg, var(--gas-primary), var(--gas-dark)); }
.card-icon { font-size: 1.5rem; }
.card-header h2 { font-size: 1.25rem; font-weight: 600; }
.card-body { padding: 20px; background: #f8fafc; }

.input-group { margin-bottom: 16px; }
.input-group:last-child { margin-bottom: 0; }
.input-group label { display: block; font-size: 0.9rem; font-weight: 500; color: var(--text-primary); margin-bottom: 6px; }
.input-group input { width: 100%; padding: 12px 16px; border: 2px solid #e2e8f0; border-radius: var(--radius-sm); font-size: 1rem; transition: border-color var(--transition-fast); background: white; }
.input-group input:focus { outline: none; border-color: var(--ev-primary); box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.1); }
.gas-card .input-group input:focus { border-color: var(--gas-primary); box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1); }
.input-hint { display: block; font-size: 0.8rem; color: var(--text-light); margin-top: 4px; }

.common-params { background: linear-gradient(135deg, #f0f9ff, #f0fdf4); border-radius: var(--radius-lg); padding: 24px; margin-bottom: 24px; }
.common-params h3 { font-size: 1.1rem; color: var(--text-primary); margin-bottom: 16px; }
.common-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
@media (max-width: 480px) { .common-grid { grid-template-columns: 1fr; } }

.result-section { border-top: 1px solid #e2e8f0; padding-top: 24px; }
.result-section h3 { text-align: center; font-size: 1.3rem; color: var(--text-primary); margin-bottom: 24px; }
.result-grid { display: grid; grid-template-columns: 1fr auto 1fr; gap: 20px; align-items: stretch; }
@media (max-width: 768px) { .result-grid { grid-template-columns: 1fr; } }

.result-card { border-radius: var(--radius-lg); overflow: hidden; box-shadow: var(--shadow-md); }
.result-header { padding: 14px 20px; display: flex; align-items: center; gap: 10px; color: white; font-weight: 600; }
.ev-result .result-header { background: linear-gradient(135deg, var(--ev-primary), var(--ev-dark)); }
.gas-result .result-header { background: linear-gradient(135deg, var(--gas-primary), var(--gas-dark)); }
.result-icon { font-size: 1.3rem; }
.result-total { padding: 20px; text-align: center; background: #f8fafc; border-bottom: 1px solid #e2e8f0; }
.total-label { display: block; font-size: 0.9rem; color: var(--text-secondary); margin-bottom: 8px; }
.total-value { font-size: 2.5rem; font-weight: 700; }
.ev-result .total-value { color: var(--ev-dark); }
.gas-result .total-value { color: var(--gas-dark); }
.total-unit { font-size: 1rem; color: var(--text-secondary); margin-left: 4px; }
.result-details { padding: 16px 20px; background: white; }
.detail-row { display: flex; justify-content: space-between; padding: 8px 0; font-size: 0.9rem; border-bottom: 1px solid #f1f5f9; }
.detail-row:last-child { border-bottom: none; }
.detail-row.highlight { color: var(--ev-dark); }
.per-km-cost { padding: 14px 20px; background: #f1f5f9; text-align: center; font-size: 0.95rem; }
.per-km-cost strong { font-size: 1.2rem; margin: 0 4px; }
.ev-result .per-km-cost strong { color: var(--ev-dark); }
.gas-result .per-km-cost strong { color: var(--gas-dark); }

.result-vs { display: flex; flex-direction: column; align-items: center; justify-content: center; padding: 20px; }
.vs-circle { width: 60px; height: 60px; background: linear-gradient(135deg, var(--ev-primary), var(--gas-primary)); border-radius: 50%; display: flex; align-items: center; justify-content: center; color: white; font-size: 1.3rem; font-weight: 700; box-shadow: var(--shadow-lg); margin-bottom: 20px; }
.savings { text-align: center; padding: 16px; background: linear-gradient(135deg, #fef3c7, #d1fae5); border-radius: var(--radius-md); min-width: 120px; }
.savings-label { display: block; font-size: 0.85rem; color: var(--text-secondary); margin-bottom: 4px; }
.savings-value { display: block; font-size: 1.5rem; font-weight: 700; color: var(--ev-dark); }
.savings-winner { display: block; font-size: 0.8rem; color: var(--text-secondary); margin-top: 4px; }

.visual-compare { margin-top: 24px; padding: 20px; background: #f8fafc; border-radius: var(--radius-md); }
.bar-label { font-size: 0.9rem; font-weight: 500; margin-bottom: 12px; color: var(--text-primary); }
.bar-container { display: flex; gap: 8px; height: 40px; background: #e2e8f0; border-radius: var(--radius-sm); overflow: hidden; }
.bar { display: flex; align-items: center; justify-content: center; color: white; font-weight: 600; font-size: 0.85rem; transition: width var(--transition-slow); min-width: 60px; }
.ev-bar { background: linear-gradient(90deg, var(--ev-primary), var(--ev-dark)); width: 50%; }
.gas-bar { background: linear-gradient(90deg, var(--gas-primary), var(--gas-dark)); width: 50%; }
.bar-text { text-shadow: 0 1px 2px rgba(0, 0, 0, 0.2); }

.ad-container { margin: 24px 0; min-height: 100px; display: flex; align-items: center; justify-content: center; background: rgba(255, 255, 255, 0.1); border-radius: var(--radius-md); }

.formula-section, .example-section, .guide-section { background: var(--card-bg); border-radius: var(--radius-xl); padding: 32px; box-shadow: var(--shadow-xl); margin-bottom: 32px; }
.formula-section h2, .example-section h2, .guide-section h2 { text-align: center; font-size: 1.5rem; color: var(--text-primary); margin-bottom: 24px; }
.formula-cards, .guide-cards { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; }
@media (max-width: 768px) { .formula-cards, .guide-cards { grid-template-columns: 1fr; } }
.formula-card, .guide-card { background: #f8fafc; border-radius: var(--radius-lg); padding: 24px; border-left: 4px solid var(--ev-primary); }
.formula-card:last-child, .guide-card:nth-child(even) { border-left-color: var(--gas-primary); }
.formula-card h3, .guide-card h3 { font-size: 1.05rem; margin-bottom: 16px; color: var(--text-primary); padding-bottom: 12px; border-bottom: 1px solid #e2e8f0; }
.formula-box { background: white; border-radius: var(--radius-sm); padding: 16px; margin-bottom: 16px; overflow-x: auto; }
.formula-box code { font-family: 'Consolas', monospace; font-size: 0.9rem; color: var(--text-primary); white-space: nowrap; }
.formula-details, .guide-card ul { list-style: none; }
.formula-details li, .guide-card li { padding: 8px 0; font-size: 0.9rem; color: var(--text-secondary); border-bottom: 1px dashed #e2e8f0; padding-left: 20px; position: relative; }
.formula-details li::before, .guide-card li::before { content: '•'; position: absolute; left: 0; color: var(--ev-primary); }
.formula-details li:last-child, .guide-card li:last-child { border-bottom: none; }
.formula-details strong, .guide-card li strong { color: var(--text-primary); }

.example-card { background: #f8fafc; border-radius: var(--radius-lg); padding: 24px; }
.example-card h3 { font-size: 1.1rem; color: var(--text-primary); margin-bottom: 20px; text-align: center; padding-bottom: 16px; border-bottom: 1px solid #e2e8f0; }
.example-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; margin-bottom: 20px; }
@media (max-width: 768px) { .example-grid { grid-template-columns: 1fr; } }
.example-item { background: white; border-radius: var(--radius-md); padding: 20px; border-top: 3px solid; }
.ev-example { border-top-color: var(--ev-primary); }
.gas-example { border-top-color: var(--gas-primary); }
.example-item h4 { font-size: 1rem; margin-bottom: 16px; color: var(--text-primary); }
.example-table { width: 100%; border-collapse: collapse; font-size: 0.85rem; }
.example-table td { padding: 10px 8px; border-bottom: 1px solid #f1f5f9; }
.example-table tr:last-child td { border-bottom: none; }
.example-table td:first-child { color: var(--text-secondary); }
.example-table td:last-child { text-align: right; font-family: 'Consolas', monospace; }
.example-table tr.highlight td { color: var(--ev-dark); }
.example-table tr.total td { background: #f8fafc; font-size: 0.95rem; }
.example-conclusion { background: linear-gradient(135deg, #fef3c7, #d1fae5); border-radius: var(--radius-md); padding: 20px; text-align: center; }
.example-conclusion p { font-size: 0.95rem; line-height: 1.8; }
.ev-color { color: var(--ev-dark); font-weight: 600; }
.gas-color { color: var(--gas-dark); font-weight: 600; }
.savings-color { color: #b45309; font-weight: 700; }

.tips-card { background: linear-gradient(135deg, #fef3c7, #fef9c3); border-radius: var(--radius-lg); padding: 24px; margin-top: 24px; }
.tips-card h3 { font-size: 1.1rem; color: #92400e; margin-bottom: 20px; }
.tips-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 16px; }
@media (max-width: 640px) { .tips-grid { grid-template-columns: 1fr; } }
.tip-item { display: flex; gap: 12px; background: white; border-radius: var(--radius-md); padding: 16px; }
.tip-icon { font-size: 1.5rem; flex-shrink: 0; }
.tip-item strong { display: block; font-size: 0.95rem; color: var(--text-primary); margin-bottom: 4px; }
.tip-item p { font-size: 0.85rem; color: var(--text-secondary); margin: 0; }

.footer { text-align: center; padding: 32px 20px; color: rgba(255, 255, 255, 0.7); font-size: 0.9rem; }
.footer a { color: var(--ev-light); text-decoration: none; }
.footer a:hover { text-decoration: underline; }
.disclaimer { margin-top: 8px; font-size: 0.8rem; color: rgba(255, 255, 255, 0.5); }

@keyframes fadeIn { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }
.calc-card, .result-card, .formula-card, .guide-card, .example-card { animation: fadeIn 0.5s ease forwards; }

@media (max-width: 640px) {
    .header h1 { font-size: 1.8rem; }
    .subtitle { font-size: 1rem; }
    .calculator-section, .formula-section, .example-section, .guide-section { padding: 20px; border-radius: var(--radius-lg); }
    .result-total .total-value { font-size: 2rem; }
    .result-vs { flex-direction: row; gap: 16px; }
    .vs-circle { width: 50px; height: 50px; font-size: 1.1rem; margin-bottom: 0; }
}