* {
        box-sizing: border-box;
        font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    }

    body {
        background: #f5f6fa;
        padding: 30px;
        color: #222;
    }

    form {
        background: white;
        padding: 25px;
        border-radius: 12px;
        box-shadow: 0 4px 20px rgba(0,0,0,0.08);
        max-width: 1200px;
        margin: auto;
    }

    table {
        width: 100%;
        border-collapse: collapse;
        overflow: hidden;
        border-radius: 8px;
    }

    thead {
        background: #333;
        color: white;
    }

    tbody tbody:nth-child(even) td {
        background-color: #000;
    }

    th {
        padding: 12px;
        text-align: center;
        font-weight: 600;
    }

    td {
        padding: 8px;
        text-align: center;
        border-bottom: 1px solid #ddd;
    }

    tbody tr:hover {
        background: #f1f5ff;
    }

    input,
    select {
        width: 100%;
        padding: 6px 8px;
        border: 1px solid #ccc;
        border-radius: 6px;
        background: white;
    }

    input[type="checkbox"] {
        width: 18px;
        height: 18px;
        cursor: pointer;
    }

    input[type="color"] {
        height: 35px;
        padding: 2px;
        cursor: pointer;
    }

    input:focus,
    select:focus {
        outline: none;
        border-color: #4a90e2;
        box-shadow: 0 0 0 2px rgba(74,144,226,0.2);
    }


    button {
        margin-top: 15px;
        padding: 10px 18px;
        border: none;
        border-radius: 8px;
        cursor: pointer;
        font-size: 15px;
        transition: 0.15s;
    }

    button:hover {
        transform: translateY(-1px);
        opacity: 0.9;
    }


    button[type="submit"] {
        background: #2563eb;
        color: white;
    }

    button[type="button"] {
        background: #e5e7eb;
        color: #111;
    }

    button:disabled {
        background: #bdbdbd;
        border-color: #bdbdbd;
        color: #666;
        cursor: not-allowed;
        opacity: 1;
    }


    .remove {
        background: #333 !important;
        color: white;
        padding: 6px 10px;
        font-size: 13px;
        margin: 0;
    }


    #courses tr {
        transition: background 0.2s;
    }


    /* Better mobile display */
    @media (max-width: 900px) {

        body {
            padding: 10px;
        }

        form {
            padding: 15px;
        }

        table {
            display: block;
            overflow-x: auto;
            white-space: nowrap;
        }
    }


.loader {
  border: 16px solid #f3f3f3;
  border-radius: 50%;
  border-top: 16px solid #3498db;
  width: 120px;
  height: 120px;
  -webkit-animation: spin 2s linear infinite; /* Safari */
  animation: spin 2s linear infinite;
}

/* Safari */
@-webkit-keyframes spin {
  0% { -webkit-transform: rotate(0deg); }
  100% { -webkit-transform: rotate(360deg); }
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}


#pdf_iframe {
    width: min(100%, 1400px);
    aspect-ratio: 297 / 210;
    border: 1px solid #ccc;
    margin: 1rem auto;
}

footer {
    margin-top: 2em;
    text-align: center
}