style.css

body {
    margin: 0;
    background-color: #222;
}

canvas {
    display: block;
}

/* Grid */
#grid {
    background-color: transparent;
    background-image: linear-gradient(0deg, transparent 24%, rgba(255, 255, 255, .05) 25%, rgba(255, 255, 255, .05) 26%, transparent 27%, transparent 74%, rgba(255, 255, 255, .05) 75%, rgba(255, 255, 255, .05) 76%, transparent 77%, transparent), linear-gradient(90deg, transparent 24%, rgba(255, 255, 255, .05) 25%, rgba(255, 255, 255, .05) 26%, transparent 27%, transparent 74%, rgba(255, 255, 255, .05) 75%, rgba(255, 255, 255, .05) 76%, transparent 77%, transparent);
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-size: 76px 76px;
    pointer-events: none;
}

#grid-legend {
    position: fixed;
    right: 10px;
    bottom: 10px;
    color: #fff;
    text-align: right;
}

/* Menu */
.menu {
    margin: 0;
    padding: 0;
    list-style-type: none;

    display: none;
    position: fixed;
    top: 0;
    left: 0;

    border: 1px solid #ffaa1d;
    background: #fff5db;
}

.menu li {
    padding: 5px;
    cursor: pointer;
}

.menu li:hover {
    background-color: #fff1b0;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;

    background: #fff5db;
}

.modal .modal-header {
    position: relative;
    background: #ffaa1d;
    padding: 5px;
    padding-right: 50px;
    cursor: move;
}

.modal .modal-header .close {
    position: absolute;
    right: 0;
    top: 0;
    bottom: 0;
    width: 20px;
    border: 0;
    background: 0;
    font-size: 15px;
    cursor: pointer;
}

.modal .modal-header .close:hover {
    color: #fff;
}

.modal .modal-body {
    padding: 5px;
    border-bottom: 1px solid;
    border-right: 1px solid;
    border-left: 1px solid;
    border-color: #ffaa1d;
}

.modal .modal-footer {
    padding: 5px;
    background: #ffaa1d;
}

/* Form */
label {
    display: block;
    font-weight: bold;
    margin-bottom: 2px;
}

input {
    margin-bottom: 10px;
}