/* ========================== Reset & Base ========================== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
    --bg:        #ffffff;
    --surface:   #f9fafb;
    --border:    #e2e5eb;
    --border-hl: #cbd0d8;
    --text:      #1e293b;
    --muted:     #64748b;
    --primary:   #6366f1;
    --primary-h: #4f46e5;
    --success:   #16a34a;
    --error:     #dc2626;
    --radius:    12px;
    --max-w:     560px;
}

html { font-size: 16px; }
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100dvh;
    display: flex;
    justify-content: center;
    padding: 2rem 1rem 3rem;
    -webkit-font-smoothing: antialiased;
}

/* ========================== App Shell ========================== */
.app {
    width: 100%;
    max-width: var(--max-w);
    display: flex;
    flex-direction: column;
    gap: 1.75rem;
}

/* ========================== Header ========================== */
header { text-align: center; }
header .logo {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 56px; height: 56px;
    border-radius: 16px;
    background: linear-gradient(135deg, var(--primary), #a855f7);
    color: #fff;
    margin-bottom: .75rem;
}
header h1 {
    font-size: 1.65rem;
    font-weight: 700;
    letter-spacing: -.02em;
}
header .subtitle {
    color: var(--muted);
    font-size: .95rem;
    margin-top: .35rem;
}

/* ========================== Tabs ========================== */
.tabs {
    display: flex;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: 0 1px 3px rgba(0,0,0,.04);
    padding: 4px;
    gap: 4px;
}
.tab {
    flex: 1;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: .45rem;
    padding: .65rem 1rem;
    border: none;
    border-radius: calc(var(--radius) - 2px);
    background: transparent;
    color: var(--muted);
    font-size: .9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all .2s;
}
.tab:hover { color: var(--text); }
.tab.active {
    background: var(--primary);
    color: #fff;
    box-shadow: 0 2px 8px rgba(99,102,241,.25);
}

/* ========================== Panels ========================== */
.panel { display: none; flex-direction: column; gap: 1.25rem; }
.panel.active { display: flex; }
.panel-desc { color: var(--muted); font-size: .9rem; line-height: 1.5; }

/* ========================== Dropzone ========================== */
.dropzone {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    gap: .35rem .6rem;
    padding: .9rem 1.2rem;
    border: 2px dashed var(--border);
    border-radius: var(--radius);
    background: var(--surface);
    box-shadow: 0 1px 3px rgba(0,0,0,.04);
    text-align: center;
    transition: border-color .2s, background .2s;
    cursor: pointer;
}
.dropzone svg { color: var(--muted); width: 22px; height: 22px; flex-shrink: 0; }
.dropzone p { color: var(--muted); font-size: .85rem; }
.dropzone span { color: var(--muted); font-size: .75rem; text-transform: uppercase; letter-spacing: .04em; }
.dropzone.drag-over {
    border-color: var(--primary);
    background: rgba(99,102,241,.08);
}
.dropzone.has-file {
    border-color: var(--success);
    border-style: solid;
}
.file-btn {
    display: inline-block;
    padding: .4rem 1rem;
    border-radius: 6px;
    background: rgba(99,102,241,.1);
    color: var(--primary);
    font-size: .85rem;
    font-weight: 500;
    cursor: pointer;
    transition: background .15s;
}
.file-btn:hover { background: rgba(99,102,241,.18); }
.file-name {
    font-size: .85rem;
    color: var(--success);
    font-weight: 500;
    min-height: 1.25rem;
    word-break: break-all;
}

/* ========================== Fields ========================== */
.field-group { display: flex; flex-direction: column; gap: .4rem; }
.field-group label {
    font-size: .8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: .04em;
    color: var(--muted);
}
.field-hint {
    font-size: .78rem;
    color: var(--muted);
    opacity: .7;
    line-height: 1.3;
}
.optional-tag {
    display: inline-block;
    font-size: .65rem;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: .04em;
    padding: .1rem .4rem;
    border-radius: 4px;
    background: rgba(99,102,241,.1);
    color: var(--primary);
    vertical-align: middle;
    margin-left: .3rem;
}
.password-wrap {
    position: relative;
    display: flex;
}
.password-wrap input {
    flex: 1;
    padding: .7rem .85rem;
    padding-right: 2.75rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--surface);
    box-shadow: 0 1px 2px rgba(0,0,0,.04);
    color: var(--text);
    font-size: .95rem;
    outline: none;
    transition: border-color .15s;
}
.password-wrap input::placeholder { color: var(--muted); opacity: .6; }
.password-wrap input:focus { border-color: var(--primary); }
.eye-btn {
    position: absolute;
    right: 8px; top: 50%;
    transform: translateY(-50%);
    background: none; border: none;
    color: var(--muted);
    cursor: pointer;
    padding: 4px;
    display: flex;
    transition: color .15s;
}
.eye-btn:hover { color: var(--text); }

/* ========================== Action Button ========================== */
.action-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: .5rem;
    width: 100%;
    padding: .8rem 1.5rem;
    border: none;
    border-radius: 8px;
    background: var(--primary);
    color: #fff;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background .15s, opacity .15s, transform .1s;
}
.action-btn:hover:not(:disabled) { background: var(--primary-h); }
.action-btn:active:not(:disabled) { transform: scale(.98); }
.action-btn:disabled { opacity: .45; cursor: not-allowed; }

/* Spinner */
.spinner {
    width: 18px; height: 18px;
    border: 2.5px solid rgba(255,255,255,.35);
    border-top-color: #fff;
    border-radius: 50%;
    animation: spin .6s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ========================== Result ========================== */
.result {
    min-height: 0;
    transition: min-height .3s;
}
.result:empty { display: none; }
.result .msg {
    display: flex;
    align-items: center;
    gap: .5rem;
    padding: .85rem 1rem;
    border-radius: 8px;
    font-size: .9rem;
    line-height: 1.4;
}
.result .msg.success {
    background: rgba(22,163,74,.06);
    border: 1px solid rgba(22,163,74,.18);
    color: var(--success);
}
.result .msg.error {
    background: rgba(220,38,38,.06);
    border: 1px solid rgba(220,38,38,.18);
    color: var(--error);
}
.download-btn {
    display: inline-flex;
    align-items: center;
    gap: .4rem;
    margin-top: .6rem;
    padding: .55rem 1.1rem;
    border: none;
    border-radius: 6px;
    background: var(--success);
    color: #fff;
    font-size: .9rem;
    font-weight: 600;
    cursor: pointer;
    transition: background .15s;
    text-decoration: none;
}
.download-btn:hover { background: #16a34a; }

/* ========================== Footer ========================== */
footer {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: .4rem;
    color: var(--muted);
    font-size: .78rem;
    text-align: center;
    line-height: 1.5;
    opacity: .7;
}
footer svg { flex-shrink: 0; }

/* ========================== Responsive ========================== */
@media (max-width: 480px) {
    body { padding: 1.25rem .75rem 2rem; }
    header h1 { font-size: 1.35rem; }
    .dropzone { padding: .75rem 1rem; }
}