:root {
    --ink: #000;
    --paper: #fff;
    --muted: #888;
    --line: #000;
    --highlight: #000;
    --highlight-bg: #f1f1f1;
}

* { box-sizing: border-box; }

html, body {
    margin: 0;
    padding: 0;
    background: var(--paper);
    color: var(--ink);
    font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
    font-weight: 300;
    -webkit-font-smoothing: antialiased;
}

main {
    max-width: 640px;
    margin: 0 auto;
    padding: 80px 24px 48px;
}

.logo {
    font-family: "Menlo", "Courier New", monospace;
    font-size: 11px;
    line-height: 1.05;
    margin: 0 0 24px;
    color: var(--ink);
    white-space: pre;
}

header h1 {
    font-size: 44px;
    font-weight: 200;
    letter-spacing: -0.02em;
    margin: 0;
    border-bottom: 1px solid var(--ink);
    padding-bottom: 16px;
}

.tagline {
    margin: 16px 0 48px;
    font-size: 14px;
    color: var(--muted);
    letter-spacing: 0.04em;
    text-transform: uppercase;
}

/* Upload form */
.upload form {
    display: block;
}

.dropzone {
    position: relative;
    border: 2px dashed var(--ink);
    background: var(--paper);
    color: var(--ink);
    padding: 48px 24px;
    text-align: center;
    cursor: pointer;
    transition: background 120ms, transform 120ms, border-color 120ms;
    outline: none;
}

.dropzone:hover,
.dropzone:focus {
    background: #fafafa;
}

.dropzone.dragover {
    background: var(--ink);
    color: var(--paper);
    transform: scale(1.01);
}

.dropzone.dragover .dz-sub,
.dropzone.dragover .dz-filename {
    color: var(--paper);
}

.dropzone.has-file {
    border-style: solid;
}

.dropzone input[type="file"] {
    position: absolute;
    inset: 0;
    opacity: 0;
    cursor: pointer;
}

.dz-inner {
    pointer-events: none;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
}

.dz-icon {
    font-family: "Menlo", "Courier New", monospace;
    font-size: 22px;
    letter-spacing: 0.15em;
    margin-bottom: 4px;
}

.dz-title {
    font-size: 16px;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    font-weight: 400;
}

.dz-sub {
    font-size: 12px;
    letter-spacing: 0.06em;
    text-transform: uppercase;
    color: var(--muted);
}

.dz-filename {
    margin-top: 8px;
    font-size: 12px;
    letter-spacing: 0.04em;
    color: var(--ink);
    word-break: break-all;
    max-width: 90%;
}

.actions {
    margin-top: 16px;
    display: flex;
    justify-content: flex-end;
}

/* Progress bar */
.progress {
    margin-top: 16px;
    border: 1px solid var(--ink);
    height: 28px;
    position: relative;
    background: var(--paper);
    overflow: hidden;
}

.progress-bar {
    position: absolute;
    top: 0; left: 0; bottom: 0;
    width: 0%;
    background: var(--ink);
    transition: width 120ms linear;
}

.progress-label {
    position: relative;
    z-index: 1;
    mix-blend-mode: difference;
    color: #fff;
    font-size: 11px;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    line-height: 28px;
    text-align: center;
}

.upload button {
    border: 1px solid var(--ink);
    background: var(--ink);
    color: var(--paper);
    padding: 14px 32px;
    font-size: 14px;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    cursor: pointer;
    font-family: inherit;
    font-weight: 400;
    transition: background 120ms, color 120ms;
}

.upload button:hover {
    background: var(--paper);
    color: var(--ink);
}

.upload button:disabled {
    opacity: 0.55;
    cursor: default;
}

.error {
    margin-top: 16px;
    padding: 12px 14px;
    border: 1px solid var(--ink);
    font-size: 13px;
}

/* Result */
.result {
    margin-top: 56px;
}

.status {
    font-size: 12px;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    padding: 12px 16px;
    margin-bottom: 24px;
    border: 1px solid var(--ink);
}

.status.ok { background: var(--paper); color: var(--ink); }
.status.bad { background: var(--ink); color: var(--paper); }

/* Board */
.board {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    aspect-ratio: 1 / 1;
    width: 100%;
    max-width: 540px;
    margin: 0 auto;
    border: 2px solid var(--ink);
    background: var(--paper);
}

.cell {
    border-right: 1px solid #bbb;
    border-bottom: 1px solid #bbb;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    font-weight: 300;
    color: var(--ink);
    aspect-ratio: 1 / 1;
}

.cell.left  { border-left: 2px solid var(--ink); }
.cell.top   { border-top: 2px solid var(--ink); }
.cell.right { border-right: 2px solid var(--ink); }
.cell.bottom{ border-bottom: 2px solid var(--ink); }

.cell.new {
    background: var(--ink);
    color: var(--paper);
    font-weight: 500;
}

.cell.error {
    background: var(--paper);
    color: var(--ink);
    font-weight: 600;
    outline: 2px solid var(--ink);
    outline-offset: -4px;
    position: relative;
}

.cell.error::after {
    content: "";
    position: absolute;
    inset: 0;
    background:
        repeating-linear-gradient(
            45deg,
            transparent 0 6px,
            rgba(0, 0, 0, 0.12) 6px 7px
        );
    pointer-events: none;
}

.error-list {
    margin: 24px 0 0;
    padding: 16px 20px;
    border: 1px solid var(--ink);
    list-style: none;
    font-size: 12px;
    letter-spacing: 0.04em;
    text-transform: uppercase;
}

.error-list li {
    padding: 4px 0;
    border-bottom: 1px dashed #ccc;
}
.error-list li:last-child { border-bottom: none; }

footer {
    margin-top: 64px;
    padding-top: 16px;
    border-top: 1px solid var(--ink);
    font-size: 11px;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--muted);
    text-align: center;
}