:root {
    --page-bg: #ffffff;
    --soft-bg: #f5f6f8;
    --text-main: #111827;
    --text-muted: #667085;
    --card-bg: #ffffff;
}

html {
    scroll-behavior: smooth;
}

body {
    background: var(--page-bg);
    color: var(--text-main);
    font-family: Arial, Helvetica, sans-serif;
}

.navbar {
    min-height: 66px;
}

.nav-link {
    font-size: 1.05rem;
    font-weight: 600;
}

.hero-section {
    padding: clamp(4rem, 9vw, 7rem) 0;
}

.feature-card,
.lab-card,
.form-card,
.info-section .card {
    background: var(--card-bg);
}

.lab-card {
    min-height: 282px;
}

.info-section {
    background: var(--soft-bg);
}

.reason-box {
    min-height: 140px;
    height: 100%;
    padding: 1.35rem;
    border-radius: 18px;
}

.reason-box p {
    margin-bottom: 0;
    color: var(--text-muted);
    font-size: 1.08rem;
    line-height: 1.55;
}

.reason-blue {
    background: #cfe1ff;
}

.reason-green {
    background: #cfe7dc;
}

.reason-yellow {
    background: #fff0bf;
}

.reason-cyan {
    background: #c9f2fb;
}

.form-section {
    background: #ffffff;
}

.form-card {
    max-width: 980px;
}

.result-section {
    background: #ffffff;
}

body.dark-theme {
    --page-bg: #111827;
    --soft-bg: #172033;
    --text-main: #f8fafc;
    --text-muted: #cbd5e1;
    --card-bg: #1f2937;
}

body.dark-theme .text-secondary {
    color: #cbd5e1 !important;
}

body.dark-theme .card,
body.dark-theme .list-group-item,
body.dark-theme .form-control,
body.dark-theme .form-select,
body.dark-theme textarea {
    background-color: #1f2937;
    color: #f8fafc;
    border-color: #334155;
}

body.dark-theme .form-control::placeholder,
body.dark-theme textarea::placeholder {
    color: #94a3b8;
}

body.dark-theme .btn-outline-dark {
    color: #f8fafc;
    border-color: #f8fafc;
}

body.dark-theme .btn-outline-secondary {
    color: #e2e8f0;
    border-color: #94a3b8;
}

body.dark-theme .reason-box {
    color: #0f172a;
}

@media (max-width: 768px) {
    .hero-section {
        padding: 3rem 0;
    }

    .display-3 {
        font-size: 2.65rem;
    }
}