@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;600;700&display=swap');

:root {
    --primary: #4F46E5;
    --primary-hover: #4338CA;
    --bg: #F3F4F6;
    --surface: #FFFFFF;
    --text-main: #111827;
    --text-muted: #6B7280;
    --border: #E5E7EB;
}

* { box-sizing: border-box; font-family: 'Inter', sans-serif; margin: 0; padding: 0; }
body { background: var(--bg); color: var(--text-main); line-height: 1.6; }

/* Navigation */
nav {
    background: var(--surface);
    padding: 15px 30px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
}
nav .brand { font-size: 1.5rem; font-weight: 700; color: var(--primary); text-decoration: none; }
nav .links a { text-decoration: none; color: var(--text-muted); font-weight: 600; margin-left: 20px; transition: color 0.3s; }
nav .links a:hover { color: var(--primary); }

/* Layouts */
.container { max-width: 1100px; margin: 40px auto; padding: 0 20px; }
.flex-center { display: flex; justify-content: center; align-items: center; min-height: 80vh; }

/* Cards & Forms */
.card {
    background: var(--surface);
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    width: 100%;
    max-width: 400px; /* For login/signup forms */
}
.card-large { max-width: 800px; margin: 0 auto; }

.card h2 { text-align: center; margin-bottom: 20px; color: var(--text-main); }

input, select, textarea {
    width: 100%; padding: 12px 15px; margin-bottom: 15px;
    border: 1px solid var(--border); border-radius: 8px;
    font-size: 1rem; transition: border 0.3s;
}
input:focus, select:focus, textarea:focus { border-color: var(--primary); outline: none; }

button {
    width: 100%; padding: 12px;
    background: var(--primary); color: white;
    border: none; border-radius: 8px; font-size: 1rem; font-weight: 600;
    cursor: pointer; transition: background 0.3s;
}
button:hover { background: var(--primary-hover); }

/* Grid for Courses */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 20px; }
.course-card {
    background: var(--surface); padding: 20px; border-radius: 12px;
    box-shadow: 0 4px 6px -1px rgba(0,0,0,0.1); display: flex; flex-direction: column;
}
.course-card h3 { margin-bottom: 10px; }
.course-card p { color: var(--text-muted); margin-bottom: 20px; flex-grow: 1; }

/* Video Player */
.video-container { background: #000; border-radius: 12px; overflow: hidden; margin-top: 20px; box-shadow: 0 10px 20px rgba(0,0,0,0.2); }
video { width: 100%; display: block; }

/* Chat Box */
.chat-container { display: flex; flex-direction: column; height: 500px; }
.chat-messages { flex-grow: 1; overflow-y: auto; padding: 20px; border: 1px solid var(--border); border-radius: 8px; background: #fafafa; margin-bottom: 15px; }
.chat-messages p { background: var(--surface); padding: 10px 15px; border-radius: 20px; margin-bottom: 10px; width: fit-content; box-shadow: 0 2px 4px rgba(0,0,0,0.05); }

/* Badges / Links */
.link-text { display: block; text-align: center; margin-top: 15px; color: var(--primary); text-decoration: none; font-weight: 600; }
.link-text:hover { text-decoration: underline; }
.badge { background: #fee2e2; color: #dc2626; padding: 5px 10px; border-radius: 20px; font-size: 0.8rem; font-weight: 700; }