:root {
    --color-primary: #1d4ed8;
    --color-primary-dark: #1737a6;
    --color-ink: #1d2327;
    --color-text: #2c3338;
    --color-border: #c3c4c7;
    --color-bg: #f0f0f1;
    --radius: 3px;
    --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    font-family: var(--font);
    background: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    font-size: 16px;
}

a { color: var(--color-primary); }

.container { max-width: 1100px; margin: 0 auto; padding: 0 24px; }

.site-header { background: var(--color-ink); border-bottom: 3px solid var(--color-primary); }
.nav { display: flex; align-items: center; justify-content: space-between; padding: 14px 24px; }
.brand {
    font-weight: 600;
    font-size: 1.15rem;
    color: #fff;
    text-decoration: none;
    letter-spacing: .2px;
}
.nav nav a {
    margin-left: 22px;
    color: #c3c4c7;
    text-decoration: none;
    font-size: .95rem;
    padding-bottom: 2px;
    border-bottom: 2px solid transparent;
    transition: border-color .15s, color .15s;
}
.nav nav a:hover { color: #fff; border-bottom-color: var(--color-primary); }

main { padding: 48px 24px; min-height: 60vh; }

.hero {
    text-align: left;
    padding: 56px 0 48px;
    border-bottom: 1px solid var(--color-border);
    margin-bottom: 40px;
}
.hero h1 { font-size: 2rem; margin: 0 0 12px; font-weight: 600; color: var(--color-ink); }
.hero p { color: #50575e; max-width: 560px; }

.btn, button.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: var(--color-primary);
    color: #fff;
    padding: 13px 26px;
    min-height: 46px;
    border-radius: var(--radius);
    border: 1px solid var(--color-primary);
    cursor: pointer;
    text-decoration: none;
    font-size: 1rem;
    font-weight: 500;
    transition: background .15s;
}
.btn:hover { background: var(--color-primary-dark); border-color: var(--color-primary-dark); }
.btn[disabled] { background: #a7aaad; border-color: #a7aaad; cursor: not-allowed; }

.btn-link {
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 10px 18px;
    color: var(--color-ink);
}
.btn-link:hover { border-color: var(--color-ink); }

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(270px, 1fr)); gap: 20px; margin-top: 24px; }
.card {
    background: #fff;
    border: 1px solid var(--color-border);
    border-left: 3px solid var(--color-primary);
    border-radius: var(--radius);
    padding: 22px;
}
.card h3 { margin-top: 0; font-size: 1.05rem; }
.card a { color: var(--color-ink); text-decoration: none; }
.card a:hover { color: var(--color-primary); }

.price { display: inline-block; margin-top: 10px; font-weight: 600; color: var(--color-primary); font-size: .95rem; }

.module {
    margin: 24px 0;
    padding: 20px;
    background: #fff;
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
}
.module h3 { margin-top: 0; border-bottom: 1px solid var(--color-border); padding-bottom: 10px; }
.lesson-list { list-style: none; padding: 0; }
.lesson-list li { padding: 8px 0; border-bottom: 1px solid #f0f0f1; }
.lesson-list li:last-child { border-bottom: none; }
.quiz-item a { color: #6d3fc0; }

.lesson-layout { display: flex; gap: 36px; }
.lesson-nav {
    width: 250px;
    flex-shrink: 0;
    background: #fff;
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 16px;
    align-self: flex-start;
}
.lesson-nav ul { list-style: none; padding: 0; margin: 6px 0 18px; }
.lesson-nav h4 { margin: 0 0 4px; font-size: .85rem; text-transform: uppercase; letter-spacing: .04em; color: #50575e; }
.lesson-nav li { padding: 6px 0; border-left: 2px solid transparent; padding-left: 8px; }
.lesson-nav li.active { border-left-color: var(--color-primary); background: #f0f3fc; }
.lesson-nav li.active a { font-weight: 600; color: var(--color-primary); }
.lesson-nav li a { text-decoration: none; color: var(--color-text); }
.lesson-content { flex: 1; background: #fff; border: 1px solid var(--color-border); border-radius: var(--radius); padding: 28px; }
.video-wrap { position: relative; padding-top: 56.25%; margin-bottom: 24px; }
.video-wrap iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; border-radius: var(--radius); }

.auth-form {
    max-width: 420px;
    margin: 0 auto;
    background: #fff;
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 32px;
}
.auth-form h1 { font-size: 1.4rem; margin-top: 0; }
.auth-form label { display: block; margin-bottom: 18px; font-weight: 500; font-size: .9rem; color: #50575e; }
.auth-form input {
    width: 100%;
    padding: 13px 14px;
    min-height: 46px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    margin-top: 6px;
    font-size: 1rem;
}
.auth-form input:focus { outline: none; border-color: var(--color-primary); box-shadow: 0 0 0 1px var(--color-primary); }

.alert { padding: 14px 18px; border-radius: var(--radius); margin-bottom: 18px; border-left: 3px solid; font-size: .95rem; }
.alert-error { background: #fcf0f1; color: #8a2424; border-left-color: #c02020; }
.alert-success { background: #edf7ed; color: #2a5e2a; border-left-color: #2a7a2a; }

.quiz-question { border: 1px solid var(--color-border); border-radius: var(--radius); padding: 20px; margin-bottom: 18px; background: #fff; }
.quiz-question legend { font-weight: 600; padding-bottom: 8px; }
.quiz-option { display: block; margin: 10px 0; font-size: 1rem; }
.quiz-option input { margin-right: 8px; }

.muted { color: #50575e; }

.site-footer { border-top: 1px solid var(--color-border); padding: 24px 0; text-align: center; color: #50575e; font-size: .9rem; margin-top: 40px; }