:root {
    --gap: 1.5rem;
    --gap-md: 0.75rem;
    --gap-sm: 0.5rem;
}

@media (max-width: 600px) {
    :root {
        --gap: 1rem;
    }
}

*,
*::before,
*::after {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: system-ui, sans-serif;
    font-size: 1rem;
    line-height: 1.5;
    color: #1a1a1a;
    background: #f5f5f5;
}

h1 {
    margin: 0;
    font-size: 1.5rem;
}

/* ── Header / Nav ── */

header {
    background: #fff;
    border-bottom: 1px solid #ddd;
    padding: 0 var(--gap);
}

nav {
    display: flex;
    align-items: center;
    height: 3.5rem;
    gap: var(--gap);
}

.nav-brand {
    font-weight: 700;
    font-size: 1.1rem;
    text-decoration: none;
    color: #1a1a1a;
}

nav a {
    text-decoration: none;
    color: #444;
}

nav a:hover {
    color: #1a1a1a;
}

/* ── Error banner ── */

#error {
    background: #fee2e2;
    color: #991b1b;
    border-bottom: 1px solid #fca5a5;
    padding: var(--gap-md) var(--gap);
    font-size: 0.9rem;
}

/* ── View container ── */

#view-container {
    max-width: 48rem;
    margin: calc(var(--gap) * 2) auto;
    padding: 0 var(--gap);
}

/* ── Main view / Study page ── */

.card {
    background: #fff;
    border: 1px solid #ddd;
    border-radius: 0.5rem;
    padding: calc(var(--gap) * 1.5);
    min-height: 10rem;
    display: flex;
    flex-direction: column;
    gap: var(--gap-md);
}

.card-front {
    margin: 0;
    font-size: 1.1rem;
    font-weight: 500;
}

.card-back {
    margin: 0;
    padding-top: var(--gap-md);
    border-top: 1px solid #eee;
    color: #444;
}

.card-actions {
    display: flex;
    gap: var(--gap-md);
    margin-top: var(--gap-md);
}

button {
    cursor: pointer;
    padding: var(--gap-sm) var(--gap);
    border: 1px solid #ccc;
    border-radius: 0.375rem;
    background: #fff;
    font-size: 0.95rem;
    transition: background 0.15s;
}

button:hover:not(:disabled) {
    background: #f0f0f0;
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.status {
    margin: var(--gap-md) 0 0;
    font-size: 0.85rem;
    color: #666;
}

/* ── Write view ── */

.write-view {
    display: flex;
    flex-direction: column;
    gap: var(--gap);
    max-width: 64rem;
}

.write-columns {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr));
    gap: var(--gap);
}

.write-columns--three {
    grid-template-columns: 1fr 1fr auto;
}

.write-col {
    display: flex;
    flex-direction: column;
    gap: var(--gap-sm);
}

.write-col label {
    font-weight: 500;
    font-size: 0.9rem;
}

.write-col textarea {
    width: 100%;
    padding: var(--gap-md);
    border: 1px solid #ddd;
    border-radius: 0.375rem;
    font-family: inherit;
    font-size: 0.95rem;
    resize: vertical;
}

.write-actions {
    display: flex;
    gap: var(--gap-md);
    margin-top: var(--gap);
}

/* ── Students view ── */

.students-add {
    display: flex;
    gap: var(--gap-md);
    margin-bottom: var(--gap);
}

.student-name-input {
    flex: 1;
    padding: var(--gap-sm) var(--gap-md);
    border: 1px solid #ddd;
    border-radius: 0.375rem;
    font-size: 0.95rem;
}

.students-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: var(--gap-sm);
}

.students-list li {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: #fff;
    border: 1px solid #ddd;
    border-radius: 0.375rem;
    padding: var(--gap-sm) var(--gap-md);
}

/* ── School-class selects ── */

.school-selects {
    display: flex;
    gap: var(--gap);
}

.school-selects label {
    display: flex;
    flex-direction: column;
    gap: var(--gap-sm);
    font-size: 0.95rem;
    color: #444;
}

.school-selects select {
    padding: var(--gap-sm) var(--gap-md);
    border: 1px solid #ddd;
    border-radius: 0.375rem;
    font-size: 0.95rem;
    background: #fff;
}

/* ── Topics selection ── */

.topics-add {
    display: flex;
    gap: var(--gap-md);
}

.topic-name-input {
    flex: 1;
    padding: var(--gap-sm) var(--gap-md);
    border: 1px solid #ddd;
    border-radius: 0.375rem;
    font-size: 0.95rem;
}

.topics-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: var(--gap-sm);
}

.topics-list li {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: #fff;
    border: 1px solid #ddd;
    border-radius: 0.375rem;
    padding: var(--gap-sm) var(--gap-md);
}

.form-group {
    margin-bottom: var(--gap);
}

.form-group label {
    display: block;
    margin-bottom: var(--gap-sm);
    font-weight: 500;
    font-size: 0.9rem;
}

.form-control {
    width: 100%;
    padding: var(--gap-sm) var(--gap-md);
    border: 1px solid #ddd;
    border-radius: 0.375rem;
    font-size: 0.95rem;
    background: #fff;
}

.selected-topics {
    margin-top: var(--gap-sm);
}

.topic-pill {
    display: inline-block;
    background: #e9ecef;
    border-radius: 4px;
    padding: 4px 8px;
    margin: 2px 4px 2px 0;
    font-size: 14px;
}

.topic-pill .remove-topic {
    margin-left: 8px;
    cursor: pointer;
    color: #dc3545;
    font-weight: bold;
}